Kebaya

China Product


Etymology

Kebaya is inspired from Arab region clothing; the Arabic word abaya means clothing.

History magellan gps devices

The earliest form of Kebaya originates in the court of the Javanese Majapahit Kingdom as a means to blend the existing female Kemban, torso wrap of the aristocratic women to be more modest and acceptable to the newly adopted Islam religion. Aceh, Riau and Johor Kingdoms and Northern Sumatra adopted the Javanese style kebaya as a means of social expression of status with the more alus or refined Javanese overlords. pioneer avic s1

The name of Kebaya as a particular clothing type was noted by the Portuguese when they landed in Indonesia. Kebaya is associated with a type of blouse worn by Indonesian women in 15th or 16th century. Prior to 1600, kebaya on Java island were considered as a sacred clothing to be worn only by royal family, aristocrats (bangsawan) and minor nobility , in an era when peasant men and many women walked publicly bare-chested. wireless data logger

Slowly it naturally spread to neighbouring areas through trade, diplomacy and social interactions to Malacca, Bali, Sumatra, Borneo, Sulawesi and the Sultanate of Sulu and Mindanao Javanese kebaya as known today were noted by Raffles in 1817, as being of silk, brocade and velvet, with the central opening of the blouse fastened by brooches, rather than button and button-holes over the torso wrap kemben, the kain (and unstitched wrap fabric several metres long erroneously termed 'sarong in English (a sarung (Malaysian accent: sarong) is stitched to form a tube, like a Western dress) After hundreds of years of regional acculturation, the garments have become highly localised expressions of ethnic culture, artistry and tailoring traditions.

The earliest photographic evidence of the kebaya as known today date from 1857 of Javanese, Peranakan and Eurasian styles.

Costume Components

The quintessential kebaya is the Javanese kebaya as known today is essentially unchanged as noted by Raffles in 1817. It consists of the blouse (kebaya) of cotton , silk, lace, brocade or velvet, with the central opening of the blouse fastened by a central brooch where the flaps of the blouse meet.

The blouse is commonly semi-transparent and worn over the torso wrap or kemben. The skirt or kain is an unstitched fabric wrap around three metres long. The term sarong in English is erroneous, the sarung (Malaysian accent: sarong) is actually stitched together to form a tube, like a Western dress- the kain is unstitched, requires a helper to dress (literally wrap) the wearer and is held in place with a string (tali), then folded this string at the waist, then held with a belt (sabuk or ikat pinggang), which may hold a decorative pocket.

Varieties

There are two main varieties. The blouse, known as baju kebaya may be of two main form: the semi-transparent straighter cut blouse of the Java, Bali and the more tightly tailored Sunda kebaya and the more Islamic compatible, plainer baju kurung is a loose-fitting, knee-length long-sleeved blouse worn in the more adherent Muslim areas- including former Kingdom of Johor-Riau (now Malaysia), Sumatra and parts of coastal Java.

In Java, Bali and Sunda, the kain is commonly batik which may be from plain stamped cotton to elaborately hand-painted batik tulis embroidered silk with gold thread. In Lampung, the kain is the traditional tapis- an elaborate gold-thread embroidered ikat with small mica discs. Sumatera, Flores, Lemata Timor, and other islands commonly use kain of ikat or songket. Sumba is famous for kain decorated with lau hada: shells and beads.

During Dutch colonization of the island, European women began wearing the less restrictive and cooler kebaya as a formal or social dress. European women wore shorter sleeve and total length cotton in prints.

The day kebaya of the Eurasians was of white cotton trimmed with European handmade lace- commonly from Bruges or Holland and black silk for evening wear.

In the Malacca region, a different variety of kebaya is called "nyonya kebaya" worn by those of Chinese ancestry: the Peranakan people. The Nyonya kebaya is different in its' famously intricately hand-beaded shoes (kasut manek) and use of kain with Chinese motive batik or imported printed or hand-painted Chinese silks.

Political Significance

The only woman present during Indonesia's Proclamation of Independence, Dutch-educated activist SK Trimurti- wore kebaya cementing it as the female dress of Nationalism.

In Japanese internment camps during the Second World War, Indonesian female prisoners refused to wear the Western dress allocated them and instead wore kebaya as a display of Nationalist and racial solidarity separate from fellow Chinese, Europeans and Eurasian inmates.

The 21st of April is celebrated in Indonesia as National Kartini Day where Raden Ayu Kartini, the female suffragist and education advocate is remembered by schoolgirls wearing traditional dress according to their region. In Java, Bali and Sunda it is the kebaya.

Cultural rivalry between Malaysian and Indonesia has given rise to media-based spats over the true ownership of the 'kebaya.

Former President Megawati Sukarnoputri is a public champion of kebaya and wears fine red kebaya whenever possible in public forums and 2009 Presidential election debates.

The Suharto-era bureaucrat wives' social organisation Dharma Wanita wears a uniform of gold kebaya, with a red sash (selendang) and stamped batik pattern on the kain unique to Dharma Wanita. The late Indonesian first lady and minor aristocrat Tien Suharto was also a prominent advocate of the kebaya.

Modern Innovations

Apart from traditional kebaya, fashion designers are looking into ways of modifying the design and making kebaya a more fashionable outfit. Casual designed kebaya can even be worn with jeans or skirts. For weddings or formal events, many designers are exploring other types of fine fabrics like laces to create a bridal kebaya.

Modern-day kebaya now incorporate modern Western tailoring innovations such as clasps, zippers and buttons- zippers being a much appreciated addition for ladies' requiring the bathroom, without requiring being literally unwrapped by a helper- to the extent the true kain is near unanimously rejected.

Other modern innovations have included the blouse baju kebaya worn without the restrictive kemben, and eve the kebaya blouse worn with slacks or made of the fabric usually for the kain panjang.

Modern kebaya blouses are also zippered at the back- for practicality and for larger frame women's busts not to literally burst out the front of their blouse.

Modern Usage

The "Singapore Girl" uniform worn by Singapore Airlines stewardesses is a rather more tight-fitting interpretation of the traditional costume by French haute couture designer Pierre Balmain in 1972, considered provocative and exploitative by some[who?] at the time.

The female uniform of Garuda Indonesia and Malaysia Airlines flight attendants are more authentic modern interpretations.[citation needed]

Notable designers

Mr Raden Mas Marga Alam- famous Javanese designer and aristocrat from the house of Paku Alam keenly sought by Indonesia's socialites and wealthy.

Raden Sirait: the designer of the sarung and kebaya for the Putri Indonesia participants.

Anne Avantie.

Alin Anuar: Creative Director of the famous kebaya label Chantiq Skaly.

Gallery

R.A. Kartini and her husband in 19th century

A modern kebaya worn by a Singapore Airline Flight Attendant

Modern kebaya for woman (left) and child (right).

An elderly Sundanese woman wearing kebaya, kain batik and batik headcloth, West Java.

See also

Indonesia portal

Culture of Indonesia

Culture of Singapore

Culture of Malaysia

References

^ a b Jill Forshee, Culture and customs of Indonesia, Greenwood Publishing Group: 2006: ISBN 0313333394: 237 pages

^ Denys Lombard (1990) (in French). Le carrefour javanais: Essai dhistoire globale (Civilisations et socits). cole des hautes tudes en sciences sociales. ISBN 2713209498. 

^ Maenmas Chavalit, Maneepin Phromsuthirak: Costumes in ASEAN: ASEAN Committee on Culture and Information: 2000: ISBN 9747102838: 293 pages

^ S A. Niessen, Ann Marie Leshkowich, Carla Jones: Re-orienting fashion: the globalization of Asian dress Berg Publishers: 2003: ISBN 1859735398, 9781859735398, 283 pages pp 206-207

^ Cattoni Reading The Kebaya paper was presented to the 15th Biennial Conference of the Asian Studies Association of Australia in Canberra 29 June-2 July 2004.

^ Michael Hitchock Indonesian Textiles: Harper Collins 1991

^ Maenmas Chavalit, Maneepin Phromsuthirak: Costumes in ASEAN: ASEAN Committee on Culture and Information: 2000: ISBN 9747102838: 293 pages

^ Panular, P. B. R. Carey, The British in Java, 1811-1816: a Javanese account : a text edition, English synopsis and commentary on British Library Additional Manuscript 12330 (Babad Bdhah ing Ngayogyakarta), British Academy by Oxford University Press: 1992, ISBN 0197260624: 611 pages

^ John Pemberton, On the subject of "Java"', Cornell University Press: 1994, ISBN 0801499631: 333 pages

^ Inger Mcabe Elliott Batik: Fabled Cloth of Java, Hong Kong Periplus: 2004

^ Mattiebelle Gittinger, To Speak with Cloth:Studies in Indonesian textiles University of California: 1989

^ Cattoni Reading The Kebaya paper was presented to the 15th Biennial Conference of the Asian Studies Association of Australia in Canberra 29 June-2 July 2004: 8

^ http://lifestyle.okezone.com/read/2008/12/16/194/174166/194/marga-alam-lelaki-dalam-bisnis-kebaya

External links

Indonesian Textiles

Reading The Kebaya

- Butik Hana- commercial Indonesian site with many interesting quality images.

v  d  e

Clothing

Materials

Cotton  Fur  Leather  Linen  Nylon  Polyester  Rayon  Silk  Spandex  Wool

Tops

Blouse  Crop top  Dress shirt  Halterneck  Henley shirt  Hoodie  Jersey  Guernsey (clothing)  Polo shirt  Shirt  Sleeveless shirt  Sweater  T-shirt  Tube top  Turtleneck

Trousers or pants

Bell-bottoms  Bermuda shorts  Bondage pants  Boxer shorts  Capri pants  Cargo pants  Culottes  Cycling shorts  Dress pants  Jeans  Jodhpurs  Overall  Parachute pants  Phat pants   Shorts  Sweatpants  Windpants

Skirts

A-line skirt  Ballerina skirt  Fustanella  Hobble skirt  Jean skirt  Job skirt  Leather skirt  Kilt  Men's skirts  Microskirt  Miniskirt  Pencil skirt  Poodle skirt  Prairie skirt  Rah-rah skirt  Sarong  Skort  Slip  Train  Wrap

Dresses

Ball gown  Cocktail dress  Evening gown  Gown  Jumper dress  Little black dress  Petticoat  Sari  Sundress  Tea gown  Wedding dress

Suits and uniforms

Academic dress  Afrocentric suit  Black tie  Buddhist monastic robe  Clerical clothing  Court dress  Gymslip  Jumpsuit  Lab coat  Mao suit  Morning dress  Pantsuit  Red Sea rig  Scrubs  Stroller  Tangzhuang  Tuxedo  White tie

Outerwear

Abaya  Academic gown  Anorak  Apron  Blazer  Cloak  Coat  Duffle coat  Frock coat  Jacket  Greatcoat  Hoodie  Opera coat  Overcoat  Pea coat  Poncho  Raincoat  Redingote  Robe  Shawl  Shrug  Ski suit  Sleeved blanket  Top coat  Trench coat  Vest  Waistcoat  Windbreaker

Underwear

Boxer briefs  Boxer shorts  Brassiere  Briefs  Compression shorts  Corselet  Corset  Knickers  Lingerie  Long underwear  Men's undergarments  Panties  Teddy  Trunks  Undershirt

Accessories

Belly chain  Belt  Bow tie  Chaps  Coin purse  Earring  Gaiters  Gloves  Handbag  Leg warmer  Leggings  Necklace  Necktie  Scarf  Stocking  Sunglasses  Suspenders  Tights

Footwear

Athletic shoe  Boot  Dress shoe  Flip-flops  Hosiery  Pump  Sandal  Shoe  Slipper  Sock

Headwear

Balaclava  Cap  Fascinator  Gaung Paung  Hat  Headband  Helmet  Hijab  Hood  Kerchief  Mantilla  Niqb  Sombrero  Turban  Ushanka  Veil

Nightwear

Babydoll  Blanket sleeper  Negligee  Nightcap  Nightgown  Nightshirt  Peignoir  Pajamas

Swimwear

Bikini  Swim diaper  Wetsuit

Clothing parts

Back closure  Buckle  Button  Buttonhole  Collar  Cuff  Elastic  Fly  Hemline  Hook-and-eye  Lapel  Neckline  Pocket  Shoulder pad  Shoulder strap  Sleeve  Snap  Strap  Velcro  Waistline  Zipper

National costume

Abaya  Aboyne dress  o b ba  o di  o t thn  Baro't saya  Barong Tagalog  Bunad  jbningurinn  Cheongsam  Dashiki  Deel  Dhoti  Dirndl  Djellaba  Gkti  Gho & Kira  Han Chinese clothing  Hanbok  Jellabiya  Jilbb  Kebaya  Kente cloth  Kilt  Kimono  Lederhosen  Sampot  Sarafan  Sari  Sarong  Scottish dress

Historical garments

Banyan  Bedgown  Bodice  Braccae  Breeches  Breeching  Brunswick  Chemise  Chiton  Chlamys  Doublet  Exomis  Farthingale  Frock  Himation  Hose  Houppelande  Jerkin  Justacorps  Palla  Peplos  Polonaise  Smock-frock  Stola  Toga  Tunic

History and surveys

Africa  Ancient Greece  Ancient Rome  Ancient world  Anglo-Saxon  Byzantine  Clothing terminology  Dress code  Early Medieval Europe  Formal wear  Han Chinese clothing  History of clothing and textiles  History of Western fashion series (1100s-2000s)  Sumptuary law  Timeline of clothing and textiles technology  Undergarments  Vietnam  Women wearing pants

See also

Adaptive clothing  Adult diaper  Bathrobe  Costume  Fashion  Ironing  Laundry  Locking clothing  Reversible garment

Categories: Indonesian clothingHidden categories: All articles with specifically-marked weasel-worded phrases | Articles with specifically-marked weasel-worded phrases from September 2009 | All articles with unsourced statements | Articles with unsourced statements from July 2009

Jennifer Meyer

China Product


en.wikipedia.org/wiki/Jennifer_Meyer)

2 children

Children dunhill lighters

Ruby Sweetheart Maguire ronson lighter

(b. 2006) candle lighter

Otis Tobias Maguire

(b. 2009)

Website

http://www.jennifermeyerjewelry.com

Jennifer Meyer Maguire (born 1977) is an American jewelry designer who first rose to prominence when her signature piece, an 18-karat gold charm in the shape of a leaf, was worn by Jennifer Aniston in the 2006 film The Break-Up.

Contents

1 Early life

2 Jennifer Meyer Jewelry

3 Personal life

4 References

5 External links

//

Early life

Meyer is the daughter of Ronald Meyer, President and COO of Universal Studios, and his first wife, Ellen. Her stepfather, from her mother's re-marriage, is Rabbi David Baron (head of the Temple Shalom for the Arts), and her stepmother, from her father's re-marriage, is Kelly Chapman. She got her start in jewelry making alongside her grandmother, Edith Meyer, who taught her the basics of making enamel jewelry when she was just six years old.

As a young adult, Meyer studied Psychology at Syracuse University, then went to work for several fashion houses in the public relations departments, first for Giorgio Armani and later for Ralph Lauren. She also worked for Glamour Magazine as an editor.

Jennifer Meyer Jewelry

Meyer returned to her jewelry making roots in 2004 when, frustrated by a search for a leaf charm for a necklace, she decided to make her own. After taking several jewelry making classes and consulting with other jewelers, Meyer designed her trademark leaf-shaped 18-karat gold charm, which to her represents "turn[ing] over a new leaf". Though Meyer has extensive Hollywood connectionser father is Universal Studios President Ron Meyer; her husband is actor Tobey Maguire--her jewelry made its national debut when a stylist picked out one of Meyer's leaf pendants for Jennifer Aniston to wear in The Break-Up. The exposure led to Meyer founding her own company, Jennifer Meyer Jewelry, and her line of rings, charms, pendants, and necklaces is distributed through such luxury stores as Barneys New York, Roseark in Los Angeles, California, and Maxfield in Beverly Hills, California.

Meyer's customers include public figures such as Jennifer Aniston, Courteney Cox, Lindsay Lohan, Kate Hudson, Nicole Kidman, Kirsten Dunst, Mara Wilson, Julia Roberts, Mischa Barton, Lara Flynn Boyle, Ali Larter, Rachel Blanchard, Gabrielle Anwar, Bonnie Hunt, Katie Holmes, Ashley Olsen, Jennifer Garner, Jennie Garth, and Demi Moore, and she was named "2007 Jeweler of the Year" in the Us Magazine "Hot Hollywood Style" issue. Her heart-shaped locket adorns the neck of Kirsten Dunst's character Mary Jane Watson as a gift from her boyfriend Peter Parker (Tobey Maguire) in Spider-Man 3.

Meyer has begun adding rubies to her jewelry collection in honor of her daughter, Ruby Sweetheart Maguire, born November 10, 2006. She told Us Magazine that she now wears a ruby every day to celebrate her daughter's life.

Personal life

Meyer met Tobey Maguire in 2003 while Maguire was shooting the movie Seabiscuit at Universal Studios, and became engaged in April 2006. Their daughter Ruby Sweetheart Maguire was born November 10, 2006. Ruby's middle name comes from a childhood nickname of Meyer's given to her by her grandmother, who died a few months before Ruby's birth. Meyer married her long-time boyfriend, actor Tobey Maguire, on September 3, 2007, in Kona, Hawaii. Their second child, son Otis Tobias Maguire was born on May 8, 2009.

Meyer is Jewish and occasionally wears a Kabbalah bracelet placed on her "as a protection" by a friend of hers.

Meyer and Maguire are both Los Angeles Lakers fans and can frequently be seen courtside at Lakers home games.

References

^ Banderas ponders 'Zorro' sequel - Entertainment News, Army Archerd, Media - Variety

^ a b c d Jennifer Meyer Sparkles, published July 12, 2006; retrieved May 1, 2007.

^ Sunshine Girl, published Fall 2006; retrieved May 1, 2007.

^ a b "The Hot Hollywood Style Special", publication date May 7, 2007.

^ The Secrets of Spider-Man 3, Premiere Magazine, January/February 2007 issue, retrieved May 1, 2007.

^ Tobey Maguire, Jennifer Meyer Have A Girl, People Magazine, published November 11, 2006; retrieved May 1, 2007

^ Tobey Maguire, Jennifer Meyer Have A Girl, People Magazine, published November 11, 2006; retrieved May 1, 2007

^ Tobey Maguire Marries Jennifer Meyer in Hawaii

External links

Jennifer Meyer Jewelry official site

Categories: 1977 births | American jewelry designers | Living people | American Jews | Syracuse University alumniHidden categories: Articles with hCards

Baltic Exchange

China Product


Current management

As of December, 2008, the current management includes:

Chief Executive: Jeremy Penn massage chair human touch

Head of Finance and Company Secretary: Duncan Bain recliner massage

Communications: Bill Lines chair cushion massager

BIFFEX

BIFFEX, the Baltic International Freight Futures Exchange - was a London-based exchange for trading ocean freight futures contracts with settlement based on the Baltic Freight Index. It started trading dry cargo freight futures contracts in 1985, and was modestly successful for some years. All contracts were cleared by the ICCH (International Commodity Clearing House), later renamed LCH (London Clearing House). A tanker freight futures contract was introduced in 1986, but never became popular and was suspended indefinitely the same year. Volumes in the dry cargo contracts dwindled over the years, and the contracts ceased trading due to lack of liquidity in 2001.

The former Baltic Exchange building

Main article: 30 St Mary Axe

The historic building was designed by Smith and Wimble and completed by George Trollope & Sons in 1903: it was subsequently listed as a Grade II* listed building.

Bombing of the exchange building

On 10 April 1992 the faade of the Exchange's offices at 30 St Mary Axe was partially demolished, and the rest of the building was extensively damaged in a Provisional Irish Republican Army bomb attack. The bomb was contained in a large white truck and consisted of a fertilizer device wrapped with a detonation cord made from Semtex. It killed three people: Paul Butt, 29, Baltic Exchange employee, Thomas Casey, 49, and 15-year old Danielle Carter.

The bomb also caused damage to surrounding buildings, many of which were also badly damaged by the Bishopsgate bombing the following year. The bomb caused 800 million worth of damage, 200 million more than the total damaged caused by the 10,000 explosions that had occurred during the Troubles in Northern Ireland up to that point.

Architectural conservationists wanted to reconstruct what remained from the bombing, as it was the last remaining exchange floor in the City of London. English Heritage, the government's statutory conservation adviser, and the City of London Corporation insisted that any redevelopment must restore the building's old faade on to St Mary Axe. Baltic Exchange, unable to afford such an expensive undertaking alone, sold the site to Trafalgar House in 1995. The remaining sculptures and masonry of the structurally unstable facade block on the site were photographed and dismantled before the sale; the interior of the Exchange Hall, which was regarded as stable was initially sealed from the elements in the hope that it would be preserved in situ in any new development, but were subsequently dismantled and stored offsite in 1995-1996.

English Heritage later discovered the damage was far more severe than they had previously thought. Accordingly, they stopped insisting on a full restoration. What remained of Exchange Hall was completely razed in 1998 with the permission of the planning minister John Prescott, over the objections of architectural preservationists, including Save Britain's Heritage who sought a judicial review of his decision.

30 St Mary Axe is now home to the building commissioned by Swiss Re, commonly referred to as "the Gherkin".

The stained glass of the Baltic Exchange war memorial, which had only suffered superficial damage in the bomb blast, has now been restored and is in the National Maritime Museum

Architectural salvage

Its classic red granite, coloured marble, Portland stone, and much of the original plaster interiors that survived the bomb were first stored in a Reading warehouse before being sold in 2003 to salvage dealer Derek Davies, who moved them to Cheshire. Davies put the elements on SalvoWEB in February 2003, finally selling the 1,000 tonnes or more to salvage dealer Dennis Buggins in late 2005. Buggins then moved the elements from Cheshire to various barns around Canterbury in Kent.

Sale of building

In June 2006 an Estonian businessman, Eerik-Niiles Kross, found the ad for the Baltic Exchange on SalvoWEB whilst trawling the web for reclaimed flooring. He and his business partner Heiti Hl bought the Baltic Exchange elements for 800,000 from Dennis Buggins of Extreme Architecture, and the 49 containers were shipped via Felixstowe to Tallinn in June 2007 where the exchange will be rebuilt in Central Tallinn. Construction is stated to start in 2008.

Notes

^ LAP Architects, lap-architects.com

^ Trollope & Colls at the National Archives, nationalarchives.gov.uk

^ Extreme Restoration article, BBC News website, 5 July 2007

^ De Barid, Ciarn (2000). Ballymurphy And The Irish War. Pluto Press. p. 325. ISBN 0-7453-1509-7. 

^ Pavilions of Splendour, heritage.co.uk

^ Historic London building to be reassembled in central Tallinn, baltictimes.com

^ Extreme architectural auction sale, salvonews.blogspot.com

^ SalvoWEB : Search results for "baltic exchange" in News - page 1, salvoweb.com

References

Huber, Mark (2001). "Ch. 9:Chartering and Operations". Tanker operations: a handbook for the person-in-charge (PIC). Cambridge, MD: Cornell Maritime Press. ISBN 0-87033-528-6. 

Turpin, Edward A.; McEwen, William A. (1980). "Ch. 18:United States Navigation Laws and Ship's Business". Merchant Marine Officers' Handbook. Centreville, MD: Cornell Maritime Press. ISBN 0-87038-056-X. 

External links

Official web site, balticexchange.com

v  d  e

Ship chartering

Agreement types

Voyage charter  Time charter  Bareboat charter  Demise charter  Affreightment

Charter-party members

Ship-owner  Ship-manager  Ship-broker  Charterer

Freight rates

Worldscale

Freight derivatives

Baltic Exchange  Imarex  Baltic Dry Index

Related topics

Tramp trade  Bill of lading

Coordinates: 513054 00449 / 51.5151N 0.0802W / 51.5151; -0.0802

Categories: Shipping management | Transport economics | Service companies of the United Kingdom | Economy of London | Futures exchanges | Former buildings and structures of the City of London | Terrorism in London | Terrorist incidents in 1992 | Relocated buildings and structuresHidden categories: Articles needing additional references from November 2008 | All articles needing additional references

Sorbitol

China Product


Uses

Sweetener

Sorbitol is a sugar substitute. It may be listed under the inactive ingredients listed for some foods and products. Sorbitol is referred to as a nutritive sweetener because it provides dietary energy: 2.6 kilocalories (11 kilojoules) per gram versus the average 4 kilocalories (17 kilojoules) for carbohydrates. It often is used in diet foods (including diet drinks and ice cream), mints, cough syrups, and sugar-free chewing gum. ground venison

It also occurs naturally in many stone fruits and berries from trees of the genus Sorbus. popcorn popper

Laxative pure cocoa powder

Sorbitol can be used as a non-stimulant laxative via an oral suspension or enema. It works by drawing water into the large intestine, thereby stimulating bowel movements. Sorbitol has been determined safe for use by the elderly, although it is not recommended without consultation with a clinician.

Medical applications

Sorbitol is used in bacterial culture media to distinguish Escherichia coli 0154:H7 from most other strains of E. coli[citation needed].

Sorbitol, combined with kayexalate, helps the body rid itself of excess potassium ions in a hyperkalaemic state. The kayexalate exchanges sodium ions for potassium ions in the bowel, while sorbitol helps to eliminate it.

Health care, food, and cosmetic uses

Sorbitol often is used in modern cosmetics as a humectant and thickener[citation needed]. Sorbitol often is used in mouthwash and toothpaste. Some transparent gels can be made only with sorbitol, as it has a refractive index sufficiently high for transparent formulations.

Sorbitol is used as a cryoprotectant additive (mixed with sucrose and sodium polyphosphates) in the manufacture of surimi, a highly refined fish paste most commonly produced from Alaska (or walleye) pollock (Theragra chalcogramma).[citation needed] It is also used as a humectant in some cigarettes.

Sorbital sometimes is used as a sweetener and humectant in cookies and other foods that are not identified as "dietary" items.

Medical importance

Even in the absence of dietary sorbitol, cells produce sorbitol naturally.

Too much sorbitol trapped in eye and nerve cells can damage these cells, leading to retinopathy and neuropathy. Substances that prevent or slow the action of aldose reductase are being studied as a way to prevent or delay these complications of diabetes. Aldose reductase is the first enzyme in the sorbitol pathway. This pathway is responsible for the conversion of glucose to sorbitol, and of galactose to galactitol. Under conditions of hyperglycemia, sorbitol accumulation occurs. Aldose reductase inhibitors prevent the accumulation of intracellular sorbitol.. Sensitivity to the substance may result in severe pain among individuals who are intolerant of it and exhibit adverse symptoms from sorbitol.

Diabetic retinopathy and neuropathy may be related to excess sorbitol in the cells of the eyes and nerves. The source of this sorbitol in diabetics is excess glucose, which goes through the sorbitol-aldose reductase pathway.

In some human enzyme deficiencies such as galactosemia, sorbitol excess arises and can cause damage to the body. In diabetes mellitus, enzyme deficiency in the lens of the eye may cause sorbitol accumulation and cataracts[citation needed].

Adverse medical effects

Sorbitol also may aggravate irritable bowel syndrome, and similar gastrointestinal conditions, resulting in severe abdominal pain for those affected, even from small amounts ingested.

Overdose effects

Ingesting large amounts of sorbitol can lead to abdominal pain, gas, and mild to severe diarrhea.[citation needed] Sorbitol ingestion of 20 grams (0.7 oz) per day as sugar-free gum has led to severe diarrhea leading to unintended weight loss of 11 kilograms (24 lb) in a woman originally weighing 52 kilograms (110 lb); another patient required hospitalization after habitually consuming 30 grams (1 oz) per day.

Compendial status

Food Chemical Codex

European Pharmacopoeia 6.1

British Pharmacopoeia 2009

Japanese Pharmacopoeia 15[citation needed]

Miscellaneous uses

A mixture of sorbitol and potassium nitrate has found some success as an amateur solid rocket fuel.

Sorbitol is identified as a potential key chemical intermediate from biomass resources. Complete reduction of sorbitol opens the way to alkanes such as hexane which can be used as a biofuel. Sorbitol itself provides much of the hydrogen required for the transformation.

19 C6H14O6 13 C6H14 + 36 CO2 + 42 H2O

The above chemical reaction is exothermic; 1.5 mole of sorbitol generates approximately 1 mole of hexane. When hydrogen is co-fed, no carbon dioxide is produced.

See also

Mannitol

Mouthwash

Xylitol

External links

NIH Diabetes dictionary see entry on sorbitol

Notes and references

^ Lehninger Principles of Biochemistry, Nelson and Cox, Fourth Edition

^ ACS :: Cancer Drug Guide: sorbitol

^ Lederle FA: Epidemiology of constipation in elderly patients. Drug utilization and cost-containment strategies. Drugs and Ageing 6:465-469, 1995.

^ Rugolotto S, Gruber M, Solano PD, Chini L, Gobbo S, Pecori S (April 2007). "Necrotizing enterocolitis in a 850 gram infant receiving sorbitol-free sodium polystyrene sulfonate (Kayexalate): clinical and histopathologic findings". J Perinatol 27 (4): 2479. doi:10.1038/sj.jp.7211677. PMID 17377608. 

^ Gallaher Group Plc - Ingredients

^ Sorbitol: a hazard for diabetics? Nutrition Health Review

^ Normalizing mitochondrial superoxide production blocks three pathways of hyperglycaemic damage.

^ Irritable Bowel Syndrome: Causes and Treatment - What can aggravate my symptoms?

^ Kathleen Doheny (2008-01-10). "Sweetener Side Effects: Case Histories". WebMD Medical News. http://www.webmd.com/diet/news/20080110/sweetener-side-effects-case-histories. Retrieved 2008-01-10. 

^ The United States Pharmacopeial Convention. "Revisions to FCC, First Supplement". http://www.usp.org/fcc/FCC61SBallotResultsWebPostingReport04.html. Retrieved 6 July 2009. 

^ Sigma Aldrich. "D-Sorbitol". http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=97336. Retrieved 6 July 2009. 

^ European Pharmacopoeia. "Index, Ph Eur". https://www.edqm.eu/store/images/majbdd/200709201618250.6_1%20IndexE.pdf. Retrieved 6 July 2009. 

^ British Pharmacopoeia (2009). "Index, BP 2009". http://www.pharmacopoeia.co.uk/pdf/2009_index.pdf. Retrieved 6 July 2009. 

^ Richard Nakka's Experimental Rocketry Web Site

^ Production of Liquid Hydrocarbons from Biomass Jrgen O. Metzger Angewandte Chemie International Edition Volume 45, Issue 5 , Pages 696 - 698 2005 link to the publisher

v  d  e

Laxatives and cathartics (A06)

Softeners, emollients

Paraffin  Docusate sodium

Contact laxatives

Oxyphenisatine  Bisacodyl  Dantron  Phenolphthalein  Castor oil  Senna glycosides  Cascara  Sodium picosulfate  Bisoxatin

Bulk producers

Ispaghula  Ethulose  Sterculia  Linseed  Methylcellulose  Triticum  Polycarbophil calcium

Osmotically acting laxatives

Magnesium carbonate  Magnesium oxide  Magnesium peroxide  Magnesium sulfate  Lactulose  Lactitol  Sodium sulfate  Pentaerythritol  Macrogol  Mannitol  Sodium phosphate  Sorbitol  Magnesium citrate  Sodium tartrate

Enemas

Sodium laurilsulfate  Sodium phosphate  Bisacodyl  Dantron  Glycerol  Oil  Sorbitol

Peripheral opioid antagonists

Alvimopan  Methylnaltrexone  Oxycodone/naloxone

Prostaglandins

Lubiprostone

v  d  e

Antianemic preparations (B03), blood substitutes and perfusion solutions (B05), and other hematological agents (B06)

Antianemic preparations

Ferrous glycine sulfate  Ferrous fumarate  Ferrous gluconate  Ferrous carbonate  Ferrous chloride  Ferrous succinate  Ferrous sulfate  Ferrous tartrate  Ferrous aspartate  Ferrous ascorbate  Ferrous iodine

Blood substitutes and perfusion solutions

Serum albumin  Dextran  Gelatin agents  Hydroxyethylstarch  Hemoglobin crosfumaril  Hemoglobin raffimer  Sorbitol

Other hematological agents

Fibrinolysin  Desoxyribonuclease  Hyaluronidase  Chymotrypsin  Trypsin  Desoxyribonuclease  Bromelain

v  d  e

Diagnostic agents (V04)

Digestive system

Diabetes

Tolbutamide  Glucose

Fat absorption

Vitamin A concentrates

Bile duct patency

Sorbitol  Magnesium sulfate  Sincalide  Ceruletide

Liver functional capacity

Galactose  Sulfobromophthalein

Gastric secretion

Cation exchange resins  Betazole  Histamine phosphate  Pentagastrin  Methylthioninium chloride  Caffeine and sodium benzoate

Exocrine pancreatic function

Secretin  Pancreozymin (cholecystokinin)  Bentiromide

Endocrine system

Pituitary function

cortisol: Metyrapone  Corticorelin

GH: Sermorelin  Somatorelin

Thyroid function

Thyrotropin  Protirelin

Fertility disturbances

Gonadorelin

Tuberculosis

Tuberculin

Renal function

Inulin and other polyfructosans  Indigo carmine  Phenolsulfonphthalein  Alsactide  Aminohippuric acid

Categories: Osmotic diuretics | Sugar alcohols | Sweeteners | ExcipientsHidden categories: Chemboxes which contain changes to watched fields | Articles needing additional references from July 2009 | All articles needing additional references | All articles with unsourced statements | Articles with unsourced statements from July 2009 | Articles with unsourced statements from October 2007 | Articles that may contain original research from June 2009 | All articles that may contain original research

Chengdu, the international Miss made to wear women's shoes to go in the world

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"In my mind, Chengdu highlights In addition to food, beauty, beauty, there are more and more internationalized Chengdu-made brands, such as the integration of the deep cultural elements in Chengdu, capital of China's women's shoes, which not only sets a Chinese shoe-making coordinates of the internationalization of the industry, but also let the world know Chengdu, Chengdu, and cultural understanding as a platform. This time, 71 countries and regions beauties will come to Chengdu, I recommend these international Meimei to China Shoes City Shoes Direct Capital Wuhou , one wearing a pair of shoes made in Chengdu, Chengdu, feeling stylish! "Yesterday, a newspaper launched" please the eyes of Chengdu, Chengdu people recommend that you highlight - invite you to a tour guide for the Miss International "interactive activities, the next day, members of the public Xiao Mr. into the hotline to the press was impressed by the tournament group also said it will try to promote the "Miss International Chengdu-made shoes to wear away the world"! online graphing calculator

This reporter learned that, while Chengdu has always been a "China's third city of fashion" and other titles, but said the real fashion trend in the past, we will look to invest in Europe and the United States, Japan, Korea and China in Beijing and Shanghai. Every seasonal uniform changes, a number of fashionable people will always watch the first time the four major Fashion Week information. However, this year there are autumn and winter fashion trend of a change, at least in what to buy shoes on this issue, we can find the answers at home - both went to the Chinese Women's Shoes City Wuhou direct sales, buy a few pairs of shoes made in Chengdu, dressed in They went into this year's autumn and winter fashion. To know that in the just ended meeting of the Cibaud, Chengdu, in accordance with 100 Blue Shoes Chupin Chengdu-made shoes, he was officiating as the country presented to heads of his wife. caculator

It is worth mentioning that Obama's wife Michelle Obama's inauguration day, a formal occasion, he pointed across a black, shoes, high heels, shallow mouth on Chengdu from this system of shoe company, is downright Chengdu-made! At present, this women's shoes in the United States selling nearly 1 million pairs. Everyone dreams of a double-Obama lady shoes, which rated the quality of a benchmark in Chengdu Shoes. casio fx calculator

Of course, the more people into the minds of readers, or at home, locked the door, Chengdu highlights cuisine, beautiful scenery, this two-day, recommended the majority of the people food, including hot pot varieties in addition to traditional tastes, there are a variety of new guise taste, nothing is not fooled, readers of both the traditional Sichuan cuisine also has new style, and the public who wished for the international Miss Burton are feeling the day three, "Mala Tang." The people Ms. Lee, said: "I want these international Meier love Chengdu, fell in love with this coming did not want to leave the city, to retain their heart, we must first retain their stomach ... ... Ha ha!"

The Black Museum

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Program format and themes

Walking through the museum, Welles would pause at one of the exhibits, and his description of an artifact served as a device to lead into a wryly-narrated dramatised tale of a brutal murder or a vicious crime. In the closing: "Now until we meet again in the same place and I tell you another tale of the Black Museum", Welles would conclude with his signature radio phrase, "I remain, as always, obediently yours".

With the story themes deriving from objects in the collection (usually with the names of the people involved changed but the facts remaining true to history), the 52 episodes had such titles as "The Tartan Scarf," "A Piece of Iron Chain," "Frosted Glass Shards" and "A Khaki Handkerchief.". An anomaly to the series was an episode called "The Letter"; this was the only story not about murder but about forgery. hardside luggage

Broadcast history pelican hard cases

In the United States, the series aired on the Mutual Network between January 1 and December 30, 1952. luggage suitcase

Beginning May 7, 1953, it was also broadcast over Radio Luxembourg sponsored by the cleaning products Dreft and Mirro. Since the BBC carried no commercials, Radio Luxembourg aired sponsored programs at night to England.

In the United States, a program of similar scope, using many of the same picked cases as The Black Museum, and nearly mirroring its broadcast run was broadcast by NBC called Whitehall 1212. The two shows were different in the respect that while Whitehall 1212 told the story of a case entirely from the point of view of the police starting from the crime scene, The Black Museum was more heavily dramatized and played out scenes of the actual murders and included scenes from the criminal's point of view.

Trivia

Two episodes, "The Car Tire" and "The Gas Receipt," were the same story with minor differences between the two. Another pair of episodes, "The Baby's Jacket" and "The Spectacles," were based on the same case, as were "The Tan Shoe" and "The Leather Bag."

Four famous murder cases were dramatized on The Black Museum: John George Haigh, the "Acid Bath Murderer"; George Joseph Smith, the "Brides in the Bath Murderer"; Adelaide Bartlett, whose husband died from chloroform poisoning; and Florence Maybrick, who used arsenic from fly-paper to allegedly murder her husband James Maybrick (who was recently suspected of being Jack the Ripper courtesy of the 1993 publication of The Diary of Jack the Ripper).

In "Open End Wrench" it's mistakenly stated that the culprit was executed in Dartmoor. No 20th century executions were carried out in Dartmoor. Built during the Napoleonic Wars to contain French and American POWs, it was, after lying idle from 1815 to 1850, later commissioned as a convict gaol and used for dangerous long-term prisoners only.

The below-listed actual cases were used as the basis for episodes of The Black Museum:

Thomas Henry Allaway - "Telegram"

Major Herbert Rowse Armstrong - "The Champagne Glass"

Elvira Dolores Barney - "The .22 Caliber Pistol"

Adelaide Bartlett - "4 Small Bottles"

Frederick Browne & Pat Kennedy - "The Car Tire" & "The Gas Receipt"

James Camb - "Spotted Bedsheet"

George Chapman - "Straight Razor"

Christopher Craig & Derek Bentley -"Two Bullets"

John Alexander Dickman - "Tan Shoe"/"Leather Bag"

Samuel Herbert Dougal - "Lady's Shoe"

Miles Giffard - "The Service Card"

Harold Greenwood - "Weed Killer"

John George Haigh - "The Jar of Acid"

Neville Heath - "The Powder Puff"

Harold Hill - "The Khaki Handkerchief"

Karl Hulton & Elizabeth Jones - "The Jack Handle"

Charles Jenkins, Christopher Geraghty & Terence Rolt - "The .32 :Caliber Bullet"

Patrick Mahon - "The Gladstone Bag"

Brighton trunk murders - "Hammerhead"

Florence Maybrick - "Meat Juice"

William Henry Podmore - "The Receipt"

Dr. Edward Pritchard - "Walking Stick"

Florence Ransom - "The Glove"

John Robinson - "The Trunk"

Alfred Arthur Rouse - "Mallet"

Edith Thompson and Frederick Bywaters - "The Sheath Knife"

August Sangret - "Brass Button"

James Townsend Saward (alias "Jim the Penman") - "Letter"

Henry Daniel Seymour - "The Claw Hammer"

George Joseph Smith - "The Bath Tub"

Madeleine Smith - "Small White Boxes"

Frederick Stewart - "The Frosted Glass Shards"

George Stoner - "Brickbat"

Norman Thorne - "The Wool Jacket" & "The Spectacles"

Pierre Vaquier - "The Dictionary"

Nurse Dorothea Waddingham - "Prescripton"

William Wallace - "Raincoat"

Robert Wood - "The Postcard"

Episodes yet to be matched with true case histories are:

Canvas Bag

Door Key

Iron Chain

Mandolin String

Notes - Kilroy was Here

Open End Wrench

Sash Cord

Shilling

Shopping Bag

Silencer

Tartan Scarf.

Listen to

The Black Museum in The Internet Archive's Old-Time Radio Collection

References

Tullet, Tom (1979), Murder Squad: Famous Cases of Scotland Yard's Murder Squad from Crippen to The Black Panther, Granada Publishing Ltd., London, ISBN 0-586-05218-6 

Fido, Martin (1986), The Murder Guide to London, Grafton Books, London, ISBN 0-586-07179-2 

Simpson (Professor), Keith (1978), Forty Years of Murder, Grafton Books, London, ISBN 0-586-05038-8 

Browne, Douglas; Tullett, Tom (1951), Bernard Spilsbury, Grafton Books, London, ISBN 0-586-05574-6 

External links

Thrilling Days of Yesteryear

The Black Museum

Categories: 1951 works | Old-time radio programs

Hard disk drive

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History

Main article: History of hard disk drives

HDDs (introduced in 1956 as data storage for an IBM accounting computer) were originally developed for use with general purpose computers. During the 1990s, the need for large-scale, reliable storage, independent of a particular device, led to the introduction of embedded systems such as RAIDs, network attached storage (NAS) systems, and storage area network (SAN) systems that provide efficient and reliable access to large volumes of data. In the 21st century, HDD usage expanded into consumer applications such as camcorders, cellphones (e.g. the Nokia N91), digital audio players, digital video players, digital video recorders, personal digital assistants and video game consoles. electric forklift

Technology electric pallet jack

Diagram of a computer hard disk drive narrow aisle truck

HDDs record data by magnetizing ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material. A typical HDD design consists of a spindle that holds one or more flat circular disks called platters, onto which the data are recorded. The platters are made from a non-magnetic material, usually aluminum alloy or glass, and are coated with a thin layer of magnetic material, typically 1020 nm in thickness for reference, standard copy paper may be between 0.07 millimetres (70,000 nm) and 0.18 millimetres (180,000 nm) thick. with an outer layer of carbon for protection. Older disks used iron(III) oxide as the magnetic material, but current disks use a cobalt-based alloy.[citation needed]

A cross section of the magnetic surface in action. In this case the binary data are encoded using frequency modulation.

The platters are spun at very high speeds. Information is written to a platter as it rotates past devices called read-and-write heads that operate very close (tens of nanometers in new drives) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. There is one head for each magnetic platter surface on the spindle, mounted on a common arm. An actuator arm (or access arm) moves the heads on an arc (roughly radially) across the platters as they spin, allowing each head to access almost the entire surface of the platter as it spins. The arm is moved using a voice coil actuator or in some older designs a stepper motor.

The magnetic surface of each platter is conceptually divided into many small sub-micrometre-sized magnetic regions, each of which is used to encode a single binary unit of information. Initially the regions were oriented horizontally, but beginning about 2005, the orientation was changed to perpendicular. Due to the polycrystalline nature of the magnetic material each of these magnetic regions is composed of a few hundred magnetic grains. Magnetic grains are typically 10 nm in size and each form a single magnetic domain. Each magnetic region in total forms a magnetic dipole which generates a highly localized magnetic field nearby. A write head magnetizes a region by generating a strong local magnetic field. Early HDDs used an electromagnet both to magnetize the region and to then read its magnetic field by using electromagnetic induction. Later versions of inductive heads included metal in Gap (MIG) heads and thin film heads. As data density increased, read heads using magnetoresistance (MR) came into use; the electrical resistance of the head changed according to the strength of the magnetism from the platter. Later development made use of spintronics; in these heads, the magnetoresistive effect was much greater than in earlier types, and was dubbed "giant" magnetoresistance (GMR). In today's heads, the read and write elements are separate, but in close proximity, on the head portion of an actuator arm. The read element is typically magneto-resistive while the write element is typically thin-film inductive.

HD heads are kept from contacting the platter surface by the air that is extremely close to the platter; that air moves at, or close to, the platter speed.[citation needed] The record and playback head are mounted on a block called a slider, and the surface next to the platter is shaped to keep it just barely out of contact. It's a type of air bearing.

In modern drives, the small size of the magnetic regions creates the danger that their magnetic state might be lost because of thermal effects. To counter this, the platters are coated with two parallel magnetic layers, separated by a 3-atom-thick layer of the non-magnetic element ruthenium, and the two layers are magnetized in opposite orientation, thus reinforcing each other. Another technology used to overcome thermal effects to allow greater recording densities is perpendicular recording, first shipped in 2005, and as of 2007 the technology was used in many HDDs.

This section may require cleanup to meet Wikipedia's quality standards. Please improve this section if you can. (December 2009)

The grain boundaries turn out to be very important in HDD design. The grains are very small and close to each other, so the coupling between adjacent grains is very strong. When one grain is magnetized, the adjacent grains tend to be aligned parallel to it or demagnetized. Then both the stability of the data and signal-to-noise ratio will be sabotaged. A clear grain boundary can weaken the coupling of the grains and subsequently increase the signal-to-noise ratio. In longitudinal recording, the single-domain grains have uniaxial anisotropy with easy axes lying in the film plane. The consequence of this arrangement is that adjacent magnets repel each other. Therefore the magnetostatic energy is so large that it is difficult to increase areal density. Perpendicular recording media, on the other hand, has the easy axis of the grains oriented perpendicular to the disk plane. Adjacent magnets attract to each other and magnetostatic energy are much lower. So, much higher areal density can be achieved in perpendicular recording. Another unique feature in perpendicular recording is that a soft magnetic underlayer are incorporated into the recording disk. This underlayer is used to conduct writing magnetic flux so that the writing is more efficient. This will be discussed in writing process. Therefore, a higher anisotropy medium film, such as L10-FePt and rare-earth magnets, can be used.

Error handling

Modern drives also make extensive use of Error Correcting Codes (ECCs), particularly Reedolomon error correction. These techniques store extra bits for each block of data that are determined by mathematical formulae. The extra bits allow many errors to be fixed. While these extra bits take up space on the hard drive, they allow higher recording densities to be employed, resulting in much larger storage capacity for user data. In 2009, in the newest drives, low-density parity-check codes (LDPC) are supplanting Reed-Solomon. LDPC codes enable performance close to the Shannon Limit and thus allow for the highest storage density available.

Typical hard drives attempt to "remap" the data in a physical sector that is going bad to a spare physical sectoropefully while the number of errors in that bad sector is still small enough that the ECC can completely recover the data without loss. The S.M.A.R.T. system counts the total number of errors in the entire hard drive fixed by ECC, and the total number of remappings, in an attempt to predict hard drive failure.

See also: file system

Architecture

A hard disk drive with the platters and motor hub removed showing the copper colored stator coils surrounding a bearing at the center of the spindle motor. The orange stripe along the side of the arm is a thin printed-circuit cable. The spindle bearing is in the center.

A typical hard drive has two electric motors, one to spin the disks and one to position the read/write head assembly. The disk motor has an external rotor attached to the platters; the stator windings are fixed in place. The actuator has a read-write head under the tip of its very end (near center); a thin printed-circuit cable connects the read-write head to the hub of the actuator. A flexible, somewhat 'U'-shaped, ribbon cable, seen edge-on below and to the left of the actuator arm in the first image and more clearly in the second, continues the connection from the head to the controller board on the opposite side.

The head support arm is very light, but also rigid; in modern drives, acceleration at the head reaches 550 Gs.

Opened hard drive with top magnet removed, showing copper head actuator coil (top right).

The silver-colored structure at the upper left of the first image is the top plate of the permanent-magnet and moving coil motor that swings the heads to the desired position (it is shown removed in the second image). The plate supports a thin neodymium-iron-boron (NIB) high-flux magnet. Beneath this plate is the moving coil, often referred to as the voice coil by analogy to the coil in loudspeakers, which is attached to the actuator hub, and beneath that is a second NIB magnet, mounted on the bottom plate of the motor (some drives only have one magnet).

The voice coil, itself, is shaped rather like an arrowhead, and made of doubly-coated coppmagnet[clarification needed] wire. The inner layer is insulation, and the outer is thermoplastic, which bonds the coil together after it's wound on a form, making it self-supporting. The portions of the coil along the two sides of the arrowhead (which point to the actuator bearing center) interact with the magnetic field, developing a tangential force that rotates the actuator. Current flowing radially outward along one side of the arrowhead, and radially inward on the other produces the tangential force. (See magnetic field#Force on a charged particle.) If the magnetic field were uniform, each side would generate opposing forces that would cancel each other out. Therefore the surface of the magnet is half N pole, half S pole, with the radial dividing line in the middle, causing the two sides of the coil to see opposite magnetic fields and produce forces that add instead of canceling. Currents along the top and bottom of the coil produce radial forces that do not rotate the head.

Capacity and access speed

PC hard disk drive capacity (in GB) over time. The vertical axis is logarithmic, so the fit line corresponds to exponential growth.

Using rigid disks and sealing the unit allows much tighter tolerances than in a floppy disk drive. Consequently, hard disk drives can store much more data than floppy disk drives and can access and transmit them faster.

As of April 2009[update], the highest capacity consumer HDDs are 2 TB.

A typical "desktop HDD" might store between 120 GB and 2 TB although rarely above 500 GB of data (based on US market data), rotate at 5,400 to 15,000 rpm, and have a media transfer rate of 0.5 Gbit/s or higher. (1 GB = 109 Byte; 1 Gbit/s = 109 bit/s)

The fastest nterprise HDDs spin at 10,000 or 15,000 rpm, and can achieve sequential media transfer speeds above 1.6 Gbit/s. and a sustained transfer rate up to 1 Gbit/s. Drives running at 10,000 or 15,000 rpm use smaller platters to mitigate increased power requirements (as they have less air drag) and therefore generally have lower capacity than the highest capacity desktop drives.

"Mobile HDDs", i.e., laptop HDDs, which are physically smaller than their desktop and enterprise counterparts, tend to be slower and have lower capacity. A typical mobile HDD spins at either 4200rpm, 5400rpm, or 7200rpm, with 5400rpm being the most prominent. 7200rpm drives tend to be more expensive and have smaller capacities, while 4200rpm models usually have very-high storage capacities. Because of physically smaller platter(s), mobile HDDs generally have lower capacity than their larger desktop counterparts.

The exponential increases in disk space and data access speeds of HDDs have enabled the commercial viability of consumer products that require large storage capacities, such as digital video recorders and digital audio players. In addition, the availability of vast amounts of cheap storage has made viable a variety of web-based services with extraordinary capacity requirements, such as free-of-charge web search, web archiving and video sharing (Google, Internet Archive, YouTube, etc.).

The main way to decrease access time is to increase rotational speed, thus reducing rotational delay, while the main way to increase throughput and storage capacity is to increase areal density. Based on historic trends, analysts predict a future growth in HDD bit density (and therefore capacity) of about 40% per year. Access times have not kept up with throughput increases, which themselves have not kept up with growth in storage capacity.

The expected random IOPS capability of any HDD can be calculated by dividing 1000 msecs by the sum of the average seek time and the average rotational latency.

The first 3.5 HDD marketed as able to store 1 TB was the Hitachi Deskstar 7K1000. It contains five platters at approximately 200 GB each, providing 1 TB (935.5 GiB) of usable space; note the difference between its capacity in decimal units (1 TB = 1012 bytes) and binary units (1 TiB = 1024 GiB = 240 bytes). Hitachi has since been joined by Samsung (Samsung SpinPoint F1, which has 3  334 GB platters), Seagate and Western Digital in the 1 TB drive market.

In September 2009, Showa Denko announced capacity improvements in platters that they manufacture for HDD makers. A single 2.5" platter is able to hold 334 GB worth of data, and preliminary results for 3.5" indicate a 750 GB per platter capacity.

Form factor

Width

Largest capacity

Platters (Max)

5.25 FH

146 mm

47 GB (1998)

14

5.25 HH

146 mm

19.3 GB (1998)

4

3.5 SATA

102 mm

2 TB (2009)

5

3.5 PATA

102 mm

750 GB (2006)

 ?

2.5 SATA

69.9 mm

1 TB (2009)

3

2.5 PATA

69.9 mm

320 GB (2009)

 ?

1.8 SATA

54 mm

320 GB (2009)

3

1.8 PATA/LIF

54 mm

240 GB (2008)

2

1.3

43 mm

40 GB (2007)

1

1 (CFII/ZIF/IDE-Flex)

42 mm

20 GB (2006)

1

0.85

24 mm

8 GB (2004)

1

Capacity measurements

A disassembled and labeled 1997 hard drive. All major components were placed on a mirror, which created the symmetrical reflections.

Raw unformatted capacity of a hard disk drive is usually quoted with SI prefixes (metric system prefixes), incrementing by powers of 1000; today that usually means gigabytes (GB) and terabytes (TB). This is conventional for data speeds and memory sizes which are not inherently manufactured in power of two sizes, as RAM and Flash memory are. Hard disks by contrast have no inherent binary size as capacity is determined by number of heads, tracks and sectors.

This can cause some confusion because some operating systems may report the formatted capacity of a hard drive using binary prefix units which increment by powers of 1024.

A one terabyte (1 TB) disk drive would be expected to hold around 1 trillion bytes (1,000,000,000,000) or 1000 GB; and indeed most 1 TB hard drives will contain slightly more than this number. However some operating system utilities would report this as around 931 GB or 953,674 MB, whereas the correct units would be 931 GiB or 953,674 MiB. (The actual number for a formatted capacity will be somewhat smaller still, depending on the file system). Following are the correct ways of reporting one Terabyte.

SI prefixes (Hard Drive)

equivalent

Binary prefixes (OS)

equivalent

1 TB (Terabytes)

1 * 10004 B

0.9095 TiB (Tebibytes)

0.9095 * 10244 B

1000 GB (Gigabytes)

1000 * 10003 B

931.3 GiB (Gibibytes)

931.3 * 10243 B

1,000,000 MB (Megabytes)

1,000,000 * 10002 B

953,674.3 MiB (Mebibytes)

953,674.3 * 10242 B

1,000,000,000 KB (Kilobytes)

1,000,000,000 * 1000 B

976,562,500 KiB (Kibibytes)

976,562,500 * 1024 B

1,000,000,000,000 B (bytes)

-

1,000,000,000,000 B (bytes)

-

Microsoft Windows reports disk capacity both in a decimal integer to 12 or more digits and in binary prefix units to three significant digits.

The capacity of an HDD can be calculated by multiplying the number of cylinders by the number of heads by the number of sectors by the number of bytes/sector (most commonly 512). Drives with the ATA interface and a capacity of eight gigabytes or more behave as if they were structured into 16383 cylinders, 16 heads, and 63 sectors, for compatibility with older operating systems. Unlike in the 1980s, the cylinder, head, sector (C/H/S) counts reported to the CPU by a modern ATA drive are no longer actual physical parameters since the reported numbers are constrained by historic operating-system interfaces and with zone bit recording the actual number of sectors varies by zone. Disks with SCSI interface address each sector with a unique integer number; the operating system remains ignorant of their head or cylinder count.

The old C/H/S scheme has been replaced by logical block addressing. In some cases, to try to "force-fit" the C/H/S scheme to large-capacity drives, the number of heads was given as 64, although no modern drive has anywhere near 32 platters.

Formatted disk overhead

For a formatted drive, the operating system's file system internal usage is another, although minor, reason why a computer hard drive or storage device's capacity may show its capacity as different from its theoretical capacity. This would include storage for, as examples, a file allocation table (FAT) or inodes, as well as other operating system data structures. This file system overhead is usually less than 1% on drives larger than 100 MB. For RAID drives, data integrity and fault-tolerance requirements also reduce the realized capacity. For example, a RAID1 drive will be about half the total capacity as a result of data mirroring. For RAID5 drives with x drives you would lose 1/x of your space to parity. RAID drives are multiple drives that appear to be one drive to the user, but provides some fault-tolerance.

A general rule of thumb to quickly convert the manufacturer's hard disk capacity to the standard Microsoft Windows formatted capacity is 0.93*capacity of HDD from manufacturer for HDDs less than a terabyte and 0.91*capacity of HDD from manufacturer for HDDs equal to or greater than 1 terabyte.

Form factors

5 full height 110 MB HDD,

2 (8.5 mm) 6495 MB HDD,

US/UK pennies for comparison.

Six hard drives with 8, 5.25, 3.5, 2.5, 1.8, and 1 disks, partially disassembled to show platters and read-write heads, with a ruler showing inches.

Before the era of PCs and small computers, hard disks were of widely varying dimensions, typically in free standing cabinets the size of washing machines (e.g. DEC RP06 Disk Drive) or designed so that dimensions enabled placement in a 19" rack (e.g. Diablo Model 31).

With increasing sales of small computers having built in floppy-disk drives (FDDs), HDDs that would fit to the FDD mountings became desirable, and this led to the evolution of the market towards drives with certain Form factors, initially derived from the sizes of 8", 5.25" and 3.5" floppy disk drives. Smaller sizes than 3.5" have emerged as popular in the marketplace and/or been decided by various industry groups.

8 inch: 9.5 in 4.624 in 14.25 in (241.3 mm 117.5 mm 362 mm)

In 1979, Shugart Associates' SA1000 was the first form factor compatible HDD, having the same dimensions and a compatible interface to the 8 FDD.

5.25 inch: 5.75 in 1.63 in 8 in (146.1 mm 41.4 mm 203 mm)

This smaller form factor, first used in an HDD by Seagate in 1980, was the same size as full height 5-inch diameter FDD, i.e., 3.25 inches high. This is twice as high as "half height" commonly used today; i.e., 1.63 in (41.4 mm). Most desktop models of drives for optical 120 mm disks (DVD, CD) use the half height 5 dimension, but it fell out of fashion for HDDs. The Quantum Bigfoot HDD was the last to use it in the late 1990s, with ow-profile (25 mm) and ltra-low-profile (20 mm) high versions.

3.5 inch: 4 in 1 in 5.75 in (101.6 mm 25.4 mm 146 mm) = 376.77344 cm

This smaller form factor, first used in an HDD by Rodime in 1984, was the same size as the "half height" 3 FDD, i.e., 1.63 inches high. Today it has been largely superseded by 1-inch high limline or ow-profile versions of this form factor which is used by most desktop HDDs.

2.5 inch: 2.75 in 0.3740.59 in 3.945 in (69.85 mm 715 mm 100 mm) = 48.895104.775 cm3

This smaller form factor was introduced by PrairieTek in 1988; there is no corresponding FDD. It is widely used today for hard-disk drives in mobile devices (laptops, music players, etc.) and as of 2008 replacing 3.5 inch enterprise-class drives. It is also used in the Xbox 360 and Playstation 3 video game consoles. Today, the dominant height of this form factor is 9.5 mm for laptop drives, but high capacity drives (750 GB and 1 TB) have a height of 12.5 mm. Enterprise-class drives can have a height up to 15 mm. Seagate has released a wafer-thin 7mm drive aimed at entry level laptops and high end netbooks in December 2009.

1.8 inch: 54 mm 8 mm 71 mm = 30.672 cm

This form factor, originally introduced by Integral Peripherals in 1993, has evolved into the ATA-7 LIF with dimensions as stated. It is increasingly used in digital audio players and subnotebooks. An original variant exists for 25 GB sized HDDs that fit directly into a PC card expansion slot. These became popular for their use in iPods and other HDD based MP3 players.

1 inch: 42.8 mm 5 mm 36.4 mm

This form factor was introduced in 1999 as IBM's Microdrive to fit inside a CF Type II slot. Samsung calls the same form factor "1.3 inch" drive in its product literature.

0.85 inch: 24 mm 5 mm 32 mm

Toshiba announced this form factor in January 2004 for use in mobile phones and similar applications, including SD/MMC slot compatible HDDs optimized for video storage on 4G handsets. Toshiba currently sells a 4 GB (MK4001MTD) and 8 GB (MK8003MTD) version and holds the Guinness World Record for the smallest hard disk drive.

3.5" and 2.5" hard disks currently dominate the market.

By 2009 all manufacturers had discontinued the development of new products for the 1.3-inch, 1-inch and 0.85-inch form factors due to falling prices of flash memory.

The inch-based nickname of all these form factors usually do not indicate any actual product dimension (which are specified in millimeters for more recent form factors), but just roughly indicate a size relative to disk diameters, in the interest of historic continuity.

Other characteristics

Data transfer rate

As of 2008, a typical 7200rpm desktop hard drive has a sustained "disk-to-buffer" data transfer rate of about 70 megabytes per second. This rate depends on the track location, so it will be highest for data on the outer tracks (where there are more data sectors) and lower toward the inner tracks (where there are fewer data sectors); and is generally somewhat higher for 10,000rpm drives. A current widely-used standard for the "buffer-to-computer" interface is 3.0 Gbit/s SATA, which can send about 300 megabyte/s from the buffer to the computer, and thus is still comfortably ahead of today's disk-to-buffer transfer rates. Data transfer rate (read/write) can be measured by writing a large file to disk using special file generator tools, then reading back the file. Transfer rate can be influenced by file system fragmentation and the layout of the files.

Seek time

Seek time currently ranges from just under 2 ms for high-end server drives, to 15 ms for miniature drives, with the most common desktop type typically being around 9 ms.[citation needed] There has not been any significant improvement in this speed for some years. Some early PC drives used a stepper motor to move the heads, and as a result had access times as slow as 80120 ms, but this was quickly improved by voice coil type actuation in the late 1980s, reducing access times to around 20 ms.

Power consumption

Power consumption has become increasingly important, not just in mobile devices such as laptops but also in server and desktop markets. Increasing data center machine density has led to problems delivering sufficient power to devices (especially for spin up), and getting rid of the waste heat subsequently produced, as well as environmental and electrical cost concerns (see green computing). Similar issues exist for large companies with thousands of desktop PCs. Smaller form factor drives often use less power than larger drives. One interesting development in this area is actively controlling the seek speed so that the head arrives at its destination only just in time to read the sector, rather than arriving as quickly as possible and then having to wait for the sector to come around (i.e. the rotational latency). Many of the hard drive companies are now producing Green Drives that require much less power and cooling. Many of these 'Green Drives' spin slower (<5400 RPM compared to 7200 RPM, 10,000 RPM, and 15,000 RPM) and also generate less waste heat.

Also in Server and Workstation systems where there might be multiple hard disk drives, there are various ways of controlling when the hard drives spin up (highest power draw).

On SCSI hard disk drives, the SCSI controller can directly control spin up and spin down of the drives.

On Parallel ATA (aka PATA) and SATA hard disk drives, some support Power-up in standby or PUIS. The hard disk drive will not spin up until the controller or system BIOS issues a specific command to do so. This limits the power draw or consumption upon power on.

On newer SATA hard disk drives, there is Staggered Spin Up feature. The hard disk drive will not spin up until the SATA Phy comes ready (communications with the host controller starts).[citation needed]

To further control or reduce power draw and consumption, the hard disk drive can be spun down to reduce its power consumption.

Audible noise

Measured in dBA, audible noise is significant for certain applications, such as PVRs, digital audio recording and quiet computers. Low noise disks typically use fluid bearings, slower rotational speeds (usually 5,400 rpm) and reduce the seek speed under load (AAM) to reduce audible clicks and crunching sounds. Drives in smaller form factors (e.g. 2.5 inch) are often quieter than larger drives .

Shock resistance

Shock resistance is especially important for mobile devices. Some laptops now include active hard drive protection that parks the disk heads if the machine is dropped, hopefully before impact, to offer the greatest possible chance of survival in such an event. Maximum shock tolerance to date is 350 Gs for operating and 1000 Gs for non-operating.

Access and interfaces

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Hard disk drives are accessed over one of a number of bus types, including parallel ATA (P-ATA, also called IDE or EIDE), Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS), and Fibre Channel. Bridge circuitry is sometimes used to connect hard disk drives to buses that they cannot communicate with natively, such as IEEE 1394, USB and SCSI.

For the ST-506 interface, the data encoding scheme as written to the disk surface was also important. The first ST-506 disks used Modified Frequency Modulation (MFM) encoding, and transferred data at a rate of 5 megabits per second. Later controllers using 2,7 RLL (or just "RLL") encoding caused 50% more data to appear under the heads compared to one rotation of an MFM drive, increasing data storage and data transfer rate by 50%, to 7.5 megabits per second.

Many ST-506 interface disk drives were only specified by the manufacturer to run at the 1/3rd lower MFM data transfer rate compared to RLL, while other drive models (usually more expensive versions of the same drive) were specified to run at the higher RLL data transfer rate. In some cases, a drive had sufficient margin to allow the MFM specified model to run at the denser/faster RLL data transfer rate (not recommended nor guaranteed by manufacturers). Also, any RLL-certified drive could run on any MFM controller, but with 1/3 less data capacity and as much as 1/3rd less data transfer rate compared to its RLL specifications.

Enhanced Small Disk Interface (ESDI) also supported multiple data rates (ESDI disks always used 2,7 RLL, but at 10, 15 or 20 megabits per second), but this was usually negotiated automatically by the disk drive and controller; most of the time, however, 15 or 20 megabit ESDI disk drives weren't downward compatible (i.e. a 15 or 20 megabit disk drive wouldn't run on a 10 megabit controller). ESDI disk drives typically also had jumpers to set the number of sectors per track and (in some cases) sector size.

Modern hard drives present a consistent interface to the rest of the computer, no matter what data encoding scheme is used internally. Typically a DSP in the electronics inside the hard drive takes the raw analog voltages from the read head and uses PRML and Reedolomon error correction to decode the sector boundaries and sector data, then sends that data out the standard interface. That DSP also watches the error rate detected by error detection and correction, and performs bad sector remapping, data collection for Self-Monitoring, Analysis, and Reporting Technology, and other internal tasks.

SCSI originally had just one signaling frequency of 5 MHz for a maximum data rate of 5 megabytes/second over 8 parallel conductors, but later this was increased dramatically. The SCSI bus speed had no bearing on the disk's internal speed because of buffering between the SCSI bus and the disk drive's internal data bus; however, many early disk drives had very small buffers, and thus had to be reformatted to a different interleave (just like ST-506 disks) when used on slow computers, such as early Commodore Amiga, IBM PC compatibles and Apple Macintoshes.

ATA disks have typically had no problems with interleave or data rate, due to their controller design, but many early models were incompatible with each other and couldn't run with two devices on the same physical cable in a master/slave setup. This was mostly remedied by the mid-1990s, when ATA's specification was standardized and the details began to be cleaned up, but still causes problems occasionally (especially with CD-ROM and DVD-ROM disks, and when mixing Ultra DMA and non-UDMA devices).

Serial ATA does away with master/slave setups entirely, placing each disk on its own channel (with its own set of I/O ports) instead.

FireWire/IEEE 1394 and USB(1.0/2.0) HDDs are external units containing generally ATA or SCSI disks with ports on the back allowing very simple and effective expansion and mobility. Most FireWire/IEEE 1394 models are able to daisy-chain in order to continue adding peripherals without requiring additional ports on the computer itself. USB however, is a point to point network and doesn't allow for daisy-chaining. USB hubs are used to increase the number of available ports and are used for devices that don't require charging since the current supplied by hubs is typically lower than what's available from the built-in USB ports.

Disk interface families used in personal computers

Notable families of disk interfaces include:

Historical bit serial interfaces connect a hard disk drive (HDD) to a hard disk controller (HDC) with two cables, one for control and one for data. (Each drive also has an additional cable for power, usually connecting it directly to the power supply unit). The HDC provided significant functions such as serial/parallel conversion, data separation, and track formatting, and required matching to the drive (after formatting) in order to assure reliability. Each control cable could serve two or more drives, while a dedicated (and smaller) data cable served each drive.

ST506 used MFM (Modified Frequency Modulation) for the data encoding method.

ST412 was available in either MFM or RLL (Run Length Limited) encoding variants.

Enhanced Small Disk Interface (ESDI) was an interface developed by Maxtor to allow faster communication between the processor and the disk than MFM or RLL.

Modern bit serial interfaces connect a hard disk drive to a host bus interface adapter (today typically integrated into the "south bridge") with one data/control cable. (As for historical bit serial interfaces above, each drive also has an additional power cable, usually direct to the power supply unit.)

Fibre Channel (FC), is a successor to parallel SCSI interface on enterprise market. It is a serial protocol. In disk drives usually the Fibre Channel Arbitrated Loop (FC-AL) connection topology is used. FC has much broader usage than mere disk interfaces, and it is the cornerstone of storage area networks (SANs). Recently other protocols for this field, like iSCSI and ATA over Ethernet have been developed as well. Confusingly, drives usually use copper twisted-pair cables for Fibre Channel, not fibre optics. The latter are traditionally reserved for larger devices, such as servers or disk array controllers.

Serial ATA (SATA). The SATA data cable has one data pair for differential transmission of data to the device, and one pair for differential receiving from the device, just like EIA-422. That requires that data be transmitted serially. Similar differential signaling system is used in RS485, LocalTalk, USB, Firewire, and differential SCSI.

Serial Attached SCSI (SAS). The SAS is a new generation serial communication protocol for devices designed to allow for much higher speed data transfers and is compatible with SATA. SAS uses a mechanically identical data and power connector to standard 3.5" SATA1/SATA2 HDDs, and many server-oriented SAS RAID controllers are also capable of addressing SATA hard drives. SAS uses serial communication instead of the parallel method found in traditional SCSI devices but still uses SCSI commands.

Word serial interfaces connect a hard disk drive to a host bus adapter (today typically integrated into the "south bridge") with one cable for combined data/control. (As for all bit serial interfaces above, each drive also has an additional power cable, usually direct to the power supply unit.) The earliest versions of these interfaces typically had a 8 bit parallel data transfer to/from the drive, but 16 bit versions became much more common, and there are 32 bit versions. Modern variants have serial data transfer. The word nature of data transfer makes the design of a host bus adapter significantly simpler than that of the precursor HDD controller.

Integrated Drive Electronics (IDE), later renamed to ATA, with the alias P-ATA ("parallel ATA") retroactively added upon introduction of the new variant Serial ATA. The original name reflected the innovative integration of HDD controller with HDD itself, which was not found in earlier disks. Moving the HDD controller from the interface card to the disk drive helped to standardize interfaces, and to reduce the cost and complexity. The 40 pin IDE/ATA connection transfers 16 bits of data at a time on the data cable. The data cable was originally 40 conductor, but later higher speed requirements for data transfer to and from the hard drive led to an "ultra DMA" mode, known as UDMA. Progressively faster versions of this standard ultimately added the requirement for an 80 conductor variant of the same cable; where half of the conductors provides grounding necessary for enhanced high-speed signal quality by reducing cross talk. The interface for 80 conductor only has 39 pins, the missing pin acting as a key to prevent incorrect insertion of the connector to an incompatible socket, a common cause of disk and controller damage.

EIDE was an unofficial update (by Western Digital) to the original IDE standard, with the key improvement being the use of direct memory access (DMA) to transfer data between the disk and the computer without the involvement of the CPU, an improvement later adopted by the official ATA standards. By directly transferring data between memory and disk, DMA eliminates the need for the CPU to copy byte per byte, therefore allowing it to process other tasks while the data transfer occurs.

Small Computer System Interface (SCSI), originally named SASI for Shugart Associates System Interface, was an early competitor of ESDI. SCSI disks were standard on servers, workstations, Commodore Amiga and Apple Macintosh computers through the mid-90s, by which time most models had been transitioned to IDE (and later, SATA) family disks. Only in 2005 did the capacity of SCSI disks fall behind IDE disk technology, though the highest-performance disks are still available in SCSI and Fibre Channel only. The length limitations of the data cable allows for external SCSI devices. Originally SCSI data cables used single ended (common mode) data transmission, but server class SCSI could use differential transmission, either low voltage differential (LVD) or high voltage differential (HVD). ("Low" and "High" voltages for differential SCSI are relative to SCSI standards and do not meet the meaning of low voltage and high voltage as used in general electrical engineering contexts, as apply e.g. to statutory electrical codes; both LVD and HVD use low voltage signals (3.3 V and 5 V respectively) in general terminology.)

Acronym or abbreviation

Meaning

Description

SASI

Shugart Associates System Interface

Historical predecessor to SCSI.

SCSI

Small Computer System Interface

Bus oriented that handles concurrent operations.

SAS

Serial Attached SCSI

Improvement of SCSI, uses serial communication instead of parallel.

ST-506

Seagate Technology

Historical Seagate interface.

ST-412

Seagate Technology

Historical Seagate interface (minor improvement over ST-506).

ESDI

Enhanced Small Disk Interface

Historical; backwards compatible with ST-412/506, but faster and more integrated.

ATA

Advanced Technology Attachment

Successor to ST-412/506/ESDI by integrating the disk controller completely onto the device. Incapable of concurrent operations.

SATA

Serial ATA

Modification of ATA, uses serial communication instead of parallel.

Integrity

An IBM HDD head resting on a disk platter. Since the drive is not in operation, the head is simply pressed against the disk by the suspension.

Close-up of a hard disk head resting on a disk platter. A reflection of the head and its suspension is visible on the mirror-like disk.

Due to the extremely close spacing between the heads and the disk surface, any contamination of the read-write heads or platters can lead to a head crash a failure of the disk in which the head scrapes across the platter surface, often grinding away the thin magnetic film and causing data loss. Head crashes can be caused by electronic failure, a sudden power failure, physical shock, wear and tear, corrosion, or poorly manufactured platters and heads.

The HDD's spindle system relies on air pressure inside the enclosure to support the heads at their proper flying height while the disk rotates. Hard disk drives require a certain range of air pressures in order to operate properly. The connection to the external environment and pressure occurs through a small hole in the enclosure (about 0.5 mm in diameter), usually with a filter on the inside (the breather filter). If the air pressure is too low, then there is not enough lift for the flying head, so the head gets too close to the disk, and there is a risk of head crashes and data loss. Specially manufactured sealed and pressurized disks are needed for reliable high-altitude operation, above about 3,000 m (10,000 feet). Modern disks include temperature sensors and adjust their operation to the operating environment. Breather holes can be seen on all disk drives they usually have a sticker next to them, warning the user not to cover the holes. The air inside the operating drive is constantly moving too, being swept in motion by friction with the spinning platters. This air passes through an internal recirculation (or "recirc") filter to remove any leftover contaminants from manufacture, any particles or chemicals that may have somehow entered the enclosure, and any particles or outgassing generated internally in normal operation. Very high humidity for extended periods can corrode the heads and platters.

For giant magnetoresistive (GMR) heads in particular, a minor head crash from contamination (that does not remove the magnetic surface of the disk) still results in the head temporarily overheating, due to friction with the disk surface, and can render the data unreadable for a short period until the head temperature stabilizes (so called "thermal asperity", a problem which can partially be dealt with by proper electronic filtering of the read signal).

Actuation of moving arm

The hard drive's electronics control the movement of the actuator and the rotation of the disk, and perform reads and writes on demand from the disk controller. Feedback of the drive electronics is accomplished by means of special segments of the disk dedicated to servo feedback. These are either complete concentric circles (in the case of dedicated servo technology), or segments interspersed with real data (in the case of embedded servo technology). The servo feedback optimizes the signal to noise ratio of the GMR sensors by adjusting the voice-coil of the actuated arm. The spinning of the disk also uses a servo motor. Modern disk firmware is capable of scheduling reads and writes efficiently on the platter surfaces and remapping sectors of the media which have failed.

Landing zones and load/unload technology

A read/write head from a circa-1998 Fujitsu 3.5" hard disk. The area pictured is approximately 2.0 mm x 3.0mm.

Microphotograph of an older generation hard disk head and slider (1990s). The size of the front face (which is the "trailing face" of the slider) is about 0.3 mm 1.0 mm. It is the location of the actual 'head' (magnetic sensors). The non-visible bottom face of the slider is about 1.0 mm 1.25 mm (so-called "nano" size) and faces the platter. It contains the lithographically micro-machined air bearing surface (ABS) that allows the slider to fly in a highly controlled fashion. One functional part of the head is the round, orange structure visible in the middle - the lithographically defined copper coil of the write transducer. Also note the electric connections by wires bonded to gold-plated pads.

Modern HDDs prevent power interruptions or other malfunctions from landing its heads in the data zone by parking the heads either in a landing zone or by unloading (i.e., load/unload) the heads. Some early PC HDDs did not park the heads automatically and they would land on data. In some other early units the user manually parked the heads by running a program to park the HDD's heads.

A landing zone is an area of the platter usually near its inner diameter (ID), where no data are stored. This area is called the Contact Start/Stop (CSS) zone. Disks are designed such that either a spring or, more recently, rotational inertia in the platters is used to park the heads in the case of unexpected power loss. In this case, the spindle motor temporarily acts as a generator, providing power to the actuator.

Spring tension from the head mounting constantly pushes the heads towards the platter. While the disk is spinning, the heads are supported by an air bearing and experience no physical contact or wear. In CSS drives the sliders carrying the head sensors (often also just called heads) are designed to survive a number of landings and takeoffs from the media surface, though wear and tear on these microscopic components eventually takes its toll. Most manufacturers design the sliders to survive 50,000 contact cycles before the chance of damage on startup rises above 50%. However, the decay rate is not linear: when a disk is younger and has had fewer start-stop cycles, it has a better chance of surviving the next startup than an older, higher-mileage disk (as the head literally drags along the disk's surface until the air bearing is established). For example, the Seagate Barracuda 7200.10 series of desktop hard disks are rated to 50,000 start-stop cycles, in other words no failures attributed to the head-platter interface were seen before at least 50,000 start-stop cycles during testing.

Around 1995 IBM pioneered a technology where a landing zone on the disk is made by a precision laser process (Laser Zone Texture = LZT) producing an array of smooth nanometer-scale "bumps" in a landing zone, thus vastly improving stiction and wear performance. This technology is still largely in use today (2008), predominantly in desktop and enterprise (3.5 inch) drives. In general, CSS technology can be prone to increased stiction (the tendency for the heads to stick to the platter surface), e.g. as a consequence of increased humidity. Excessive stiction can cause physical damage to the platter and slider or spindle motor.

Load/Unload technology relies on the heads being lifted off the platters into a safe location, thus eliminating the risks of wear and stiction altogether. The first HDD RAMAC and most early disk drives used complex mechanisms to load and unload the heads. Modern HDDs use ramp loading, first introduced by Memorex in 1967, to load/unload onto plastic "ramps" near the outer disk edge.

All HDDs today still use one of these two technologies listed above. Each has a list of advantages and drawbacks in terms of loss of storage area on the disk, relative difficulty of mechanical tolerance control, non-operating shock robustness, cost of implementation, etc.

Addressing shock robustness, IBM also created a technology for their ThinkPad line of laptop computers called the Active Protection System. When a sudden, sharp movement is detected by the built-in accelerometer in the Thinkpad, internal hard disk heads automatically unload themselves to reduce the risk of any potential data loss or scratch defects. Apple later also utilized this technology in their PowerBook, iBook, MacBook Pro, and MacBook line, known as the Sudden Motion Sensor. Sony, HP with their HP 3D DriveGuard and Toshiba have released similar technology in their notebook computers.

This accelerometer based shock sensor has also been used for building cheap earthquake sensor networks.

Disk failures and their metrics

Wikibooks has a book on the topic of

Minimizing hard disk drive failure and data loss

Most major hard disk and motherboard vendors now support S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology), which measures drive characteristics such as operating temperature, spin-up time, data error rates, etc. Certain trends and sudden changes in these parameters are thought to be associated with increased likelihood of drive failure and data loss.

However, not all failures are predictable. Normal use eventually can lead to a breakdown in the inherently fragile device, which makes it essential for the user to periodically back up the data onto a separate storage device. Failure to do so will lead to the loss of data. While it may sometimes be possible to recover lost information, it is normally an extremely costly procedure, and it is not possible to guarantee success. A 2007 study published by Google suggested very little correlation between failure rates and either high temperature or activity level; however, the correlation between manufacturer/model and failure rate was relatively strong. Statistics in this matter is kept highly secret by most entities. Google did not publish the manufacturer's names along with their respective failure rates, though they have since revealed that they use Hitachi Deskstar drives in some of their servers. While several S.M.A.R.T. parameters have an impact on failure probability, a large fraction of failed drives do not produce predictive S.M.A.R.T. parameters. S.M.A.R.T. parameters alone may not be useful for predicting individual drive failures.

A common misconception is that a colder hard drive will last longer than a hotter hard drive. The Google study seems to imply the reverse"lower temperatures are associated with higher failure rates". Hard drives with S.M.A.R.T.-reported average temperatures below 27 C (80.6 F) had higher failure rates than hard drives with the highest reported average temperature of 50 C (122 F), failure rates at least twice as high as the optimum S.M.A.R.T.-reported temperature range of 36 C (96.8 F) to 47 C (116.6 F).

SCSI, SAS and FC drives are typically more expensive and are traditionally used in servers and disk arrays, whereas inexpensive ATA and SATA drives evolved in the home computer market and were perceived to be less reliable. This distinction is now becoming blurred.

The mean time between failures (MTBF) of SATA drives is usually about 600,000 hours (some drives such as Western Digital Raptor have rated 1.2 million hours MTBF), while SCSI drives are rated for upwards of 1.5 million hours.[citation needed] However, independent research indicates that MTBF is not a reliable estimate of a drive's longevity. MTBF is conducted in laboratory environments in test chambers and is an important metric to determine the quality of a disk drive before it enters high volume production. Once the drive product is in production, the more valid metric is annualized failure rate (AFR).[citation needed] AFR is the percentage of real-world drive failures after shipping.

SAS drives are comparable to SCSI drives, with high MTBF and high reliability.[citation needed]

Enterprise S-ATA drives designed and produced for enterprise markets, unlike standard S-ATA drives, have reliability comparable to other enterprise class drives.

Typically enterprise drives (all enterprise drives, including SCSI, SAS, enterprise SATA and FC) experience between 0.70%-0.78% annual failure rates from the total installed drives.[citation needed]

Eventually all mechanical hard disk drives fail. And thus the strategy to mitigate loss of data is to have redundancy in some form, like RAID and backup. RAID should never be relied on as backup, as RAID controllers also break down, making the disks inaccessible. Following a backup strategy; for example, daily differential and weekly full backups, is the only sure way to prevent data loss.

Manufacturers

A Western Digital 3.5 inch 250 GB SATA HDD. This specific model features both SATA and Molex power inputs.

Seagate's hard disk drives being manufactured in a factory in Wuxi, China

See also List of defunct hard disk manufacturers

The technological resources and know-how required for modern drive development and production mean that as of 2010, virtually all of the world's HDDs are manufactured by just five large companies: Seagate, Western Digital, Hitachi, Samsung, and Toshiba.

Dozens of former HDD manufacturers have gone out of business, merged, or closed their HDD divisions; as capacities and demand for products increased, profits became hard to find, and the market underwent significant consolidation in the late 1980s and late 1990s. The first notable casualty of the business in the PC era was Computer Memories Inc. or CMI; after an incident with faulty 20 MB AT disks in 1985, CMI's reputation never recovered, and they exited the HDD business in 1987. Another notable failure was MiniScribe, who went bankrupt in 1990 after it was found that they had engaged in accounting fraud and inflated sales numbers for several years. Many other smaller companies (like Kalok, Microscience, LaPine, Areal, Priam and PrairieTek) also did not survive the shakeout, and had disappeared by 1993; Micropolis was able to hold on until 1997, and JTS, a relative latecomer to the scene, lasted only a few years and was gone by 1999, after attempting to manufacture HDDs in India. Their claim to fame was creating a new 3 form factor drive for use in laptops. Quantum and Integral also invested in the 3 form factor; but eventually ceased support as this form factor failed to catch on. Rodime was also an important manufacturer during the 1980s, but stopped making disks in the early 1990s amid the shakeout and now concentrates on technology licensing; they hold a number of patents related to 3.5-inch form factor HDDs.

The following is the genealogy of the current HDD Companies

1967: Hitachi enters the HDD business.

1967: Toshiba enters the HDD business.

1979: Seagate Technology is founded by a group of ex-IBM and ex-Memorex persons.

1988: Western Digital (WDC), then a well-known controller designer enters the HDD business by acquiring Tandon Corporation's disk manufacturing division.

1989: Seagate Technology purchases Control Data's HDD business.

1990: Maxtor purchases MiniScribe out of bankruptcy, making it the core of its low-end HDDs.

1994: Quantum purchases DEC's storage division, giving it a high-end disk range to go with its more consumer-oriented ProDrive range.

1996: Seagate acquires Conner Peripherals in a merger.

2000: Maxtor acquires Quantum's HDD business; Quantum remains in the tape business.

2003: Hitachi acquires the majority of IBMs disk division, who renamed it Hitachi Global Storage Technologies (HGST).

2006: Seagate acquires Maxtor.

2009: Toshiba acquires Fujitsu's HDD division

Sales

In the year 2007 516.2 million hard disks were sold .

See also

Automatic Acoustic Management

Binary prefix (KiB, MiB, GiB, etc.)

Click of death

Data erasure

Disk formatting

Drive mapping

du (Unix disk usage program)

External hard disk drive

File System

HDD recorder

History of hard disk drives

Hybrid drive

IBM 305 RAMAC

kilobyte, megabyte, gigabyte definitions

Multimedia

Solid-state drive

Spintronics

Write precompensation

References

^ This is the original filing date of the application which led to US Patent 3,503,060, generally accepted as the definitive disk drive patent; see, Kean, David W., "IBM San Jose, A Quarter Century Of Innovation, 1977.

^ Other terms use to describe hard disk drives include disk drive , disk file, DASD (Direct Access Storage Device), fixed disk, CKD disk and Winchester Disk Drive (after the IBM 3340).

^ Webopedia.com

^ Techtarget.com

^ How Hard Disks Work, howstuffworks.com

^ In the 1990s there was a partial return to the use of removable hard disks, such as the Iomega Jaz and Rev drives and disks and the SyQuest SyJet and Sparq drives and disks, and the Castlewood Orb drive and disk, among other models, but as of 2009 these are mostly defunct.

^ IBM.com IBM 350 disk storage unit

^ "Thickness of a Piece of Paper", HyperTextbook.com

^ "IBM OEM MR Head | Technology | The era of giant magnetoresistive heads". Hitachigst.com. 2001-08-27. http://www.hitachigst.com/hdd/technolo/gmr/gmr.htm. Retrieved 2009-03-13. 

^ Brian Hayes, Terabyte Territory, American Scientist, Vol 90 No 3 (May-June 2002) p. 212

^ "Press Releases December 14, 2004". Toshiba. http://www.toshiba.co.jp/about/press/2004_12/pr1401.htm. Retrieved 2009-03-13. 

^ "Seagate Momentus 2" HDDs per webpage Jan 2008". Seagate.com. 2008-10-24. http://www.seagate.com/www/en-us/products/laptops/momentus/. Retrieved 2009-03-13. 

^ "Seagate Baracuda 3" HDDs per webpage January 2008". Seagate.com. http://www.seagate.com/www/en-us/products/desktops/barracuda_hard_drives/. Retrieved 2009-03-13. 

^ "Western Digital Scorpio 2" and Greenpower 3" HDDs per quarterly conference, July 2007". Wdc.com. http://www.wdc.com/en/company/investor/q108remarks.asp. Retrieved 2009-03-13. 

^ Storage Review - Error Correcting Code

^ Hitachi - "Iterative Detection Read Channel Technology in Hard Disk Drives"

^ Murph, Darren (2009-01-26). "Western Digital's 2TB Caviar Green HDD on sale in Australia". Engadget.com. http://www.engadget.com/2009/01/26/western-digitals-2tb-caviar-green-hdd-on-sale-in-australia. Retrieved 2009-03-13. 

^ PC Magazine comparison of 136 desktops shows 60 in this HDD capacity range with 50 larger and 26 smaller capacities), PCMag.com

^ a b Seagate Cheetah 15K.5

^ Walter, Chip (July 25, 2005). "Kryder's Law". Scientific American (Verlagsgruppe Georg von Holtzbrinck GmbH). http://www.sciam.com/article.cfm?articleID=000B0C22-0805-12D8-BDFD83414B7F0000&ref=sciam&chanID=sa006. Retrieved 2006-10-29. 

^ "Seagate Outlines the Future of Storage :: Articles :: www.hardwarezone.com". www.hardwarezone.com<!. 2006-01-27. http://www.hardwarezone.com/articles/view.php?cid=1&id=1805&pg=2. Retrieved 2009-03-13. 

^ "Hitachi's 7K1000 Terabyte Hard Drive". Tomshardware.com. http://www.tomshardware.com/2007/04/17/hitachi_7k1000_terabyte_hard_drive/. Retrieved 2009-03-13. 

^ "Seagate, Samsung Begin to Ship 1 TB Desktop Hard Drives". Dailytech.com. http://www.dailytech.com/Article.aspx?newsid=7740. Retrieved 2009-03-13. 

^ "WD Caviar GP: The "Green" 1 TB Drive". Tomshardware.com. http://www.tomshardware.com/2007/10/11/wd_caviar_gp/. Retrieved 2009-03-13. 

^ "SDK Starts Shipments of 2.5-Inch 334 GB HD Media". http://www.sdk.co.jp/aa/english/news/2009/aanw_09_1152.html. Retrieved 2009-09-15. 

^ Seagate Elite 47, shipped 12/97 per 1998 Disk/Trend Report - Rigid Disk Drives

^ Quantum Bigfoot TS, shipped 10/98 per 1999 Disk/Trend Report - Rigid Disk Drives

^ The Quantum Bigfoot TS used a maximum of 3 platters, other earlier and lower capacity product used up to 4 platters in a 5.25 HH form factor, e.g. Microscience HH1090 circa 1989.

^ Murphy, David. "Western Digital Launches World-First 2TB Hard Drive". PC World. http://www.pcworld.com/article/158374/Western_Digital_Launches_WorldFirst_2TB_Hard_Drive.html?tk=rss_news. Retrieved 2009-01-27. 

^ "Seagate PATA (EIDE) desktop hard disk drives". http://www.seagate.com/ww/v/index.jsp?name=DB35_Series_7200.3-UltraATA-100_750GB-8_ST3750840ACE&vgnextoid=6828cd2655bfd010VgnVCM100000dd04090aRCRD&locale=en-US. 

^ "WD ships industry's first 2.5-inch 1TB hard drive". http://www.engadget.com/2009/07/27/wd-ships-industrys-first-2-5-inch-1tb-hard-drive/. 

^ "WD Scorpio BLUE 320 GB PATA Hard Drives". http://www.wdc.com/cN/products/products.asp?DriveID=599. 

^ "Toshiba Storage Solutions - MK3233GSG". http://www.toshiba.co.jp/about/press/2009_11/pr0501.htm. 

^ "Toshiba Storage Solutions - MK2431GAH". http://www.storage.toshiba.eu/index.php?id=87&pid=242&sid=7. 

^ "SDK Starts Shipments of 1.3-Inch PMR-Technology-Based HD Media". Sdk.co.jp. 2008-01-10. http://www.sdk.co.jp/aa/english/news/2008/aanw_08_0812.html. Retrieved 2009-03-13. 

^ "Toshiba's World Smallest Hard Disk Drive". Toshibastorage.com. http://www.toshibastorage.com/main.aspx?Path=StorageSolutions/0.85-inchHardDiskDrives/MK4001MTD/MK4001MTDSpecifications. Retrieved 2009-03-13. 

^ "One Drive, Multiple Applications - Tom's Hardware : WD's New Raptor Drive Is a Bird of Prey!". Tomshardware.com. 2008-04-21. http://www.tomshardware.com/reviews/HDD-SATA-VelociRaptor,1914-6.html. Retrieved 2009-03-13. 

^ "Seagate Unveils World's Thinnest 2.5-Inch Hard Drive For Slim Laptop Computers". physorg.com. 2009-12-15. http://www.physorg.com/news180118264.html. Retrieved 2009-12-15. 

^ 1.3 HDD Product Specification, Samsung, 2008

^ Toshiba's 0.85-inch HDD is set to bring multi-gigabyte capacities to small, powerful digital products, Toshiba press release, January 8, 2004

^ Toshiba enters Guinness World Records Book with the world's smallest hard disk drive, Toshiba press release, March 16, 2004

^ Flash price fall shakes HDD market, EETimes Asia, August 1, 2007.

^ In 2008 Samsung introduced the 1.3-inch SpinPoint A1 HDD but by March 2009 the family was listed as End Of Life Products and new new 1.3-inch models were not available in this size.

^ "WD Caviar Blue: Drive Specifications (250750 GB SATA)" (PDF). Document Library. Western Digital. June 2008. p. 2. http://wdc.com/en/library/sata/2879-701277.pdf. Retrieved 2009-06-27. 

^ Momentus 5400.5 SATA 3Gb/s 320-GB Hard Drive

^ "Reed Solomon Codes - Introduction"

^ Micro House PC Hardware Library Volume I: Hard Drives, Scott Mueler, Macmillan Computer Publishing

^ Waea.org, Ruggedized Disk Drives for Commercial Airborne Computer Systems

^ Barracuda 7200.10 Serial ATA Product Manual

^ IEEE.org, IEEE Trans. Magn.

^ Pugh et al.; "IBM's 360 and Early 370 Systems"; MIT Press, 1991, pp.270

^ "Sony | For Business | VAIO SMB". B2b.sony.com. http://b2b.sony.com/Solutions/lpage.do?page=/vaio_smb/index.html&name=VAIO%20SMB. Retrieved 2009-03-13. 

^ HP.com

^ Toshiba HDD Protection measures.

^ "Quake-Catcher Network". http://qcn.stanford.edu/.  090128 qcn.stanford.edu

^ a b c d Eduardo Pinheiro, Wolf-Dietrich Weber and Luiz Andr Barroso (February 2007). "Failure Trends in a Large Disk Drive Population". 5th USENIX Conference on File and Storage Technologies (FAST 2007). USENIX Conference on File and Storage Technologies. http://labs.google.com/papers/disk_failures.html. Retrieved 2008-09-15. 

^ CNet.com

^ "Everything You Know About Disks Is Wrong". StorageMojo. February 20, 2007. http://storagemojo.com/?p=383. Retrieved 2007-08-29. 

^ "Differences between an Enterprise-Class HDD and a Desktop-Class HDD". Synology.com. 2008-09-04. http://www.synology.com/wiki/index.php/Differences_between_an_Enterprise-Class_HDD_and_a_Desktop-Class_HDD. Retrieved 2009-03-13. 

^ Intel Whitepaper on Enterprise-class versus Desktop-class Hard Drives

^ Apparently the CMI disks suffered from a higher soft error rate than IBM's other suppliers (Seagate and MiniScribe) but the bugs in Microsoft's DOS Operating system may have turned these recoverable errors into hard failures. At some point, possibly MS-DOS 3.0, soft errors were reported as disk hard errors and a subsequent Microsoft patch turned soft errors into corrupted memory with unpredictable results ("crashes"). MS-DOS 3.3 apparently resolved this series of problems but by that time it was too late for CMI. See also, "IBM and CMI in Joint Effort to Rehab AT Hard-Disk Rejects", PC Week, v.2 n.11, p.1, March 19, 1985

^ "Company News; Tandon Sells Disk Driv...