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Encyclopedia > Hard disk
Hard Disk Drive

An IBM hard disk drive with the metal cover removed. The platters are highly reflective.
Date Invented: September 13, 1956
Invented By: Reynold Johnson
Connects to:
  • Controller (typically on motherboard) via one of
    • PATA (IDE) interface
    • SATA interface
    • SCSI interface
    • SAS interface
Market Segments:
  • Desktop
  • Mobile
  • Enterprise
  • Consumer
  • Other/Miscellaneous
The inside of a hard disk drive displaying the actuator arm traveling over the top platter
The inside of a hard disk drive displaying the actuator arm traveling over the top platter

A hard disk (commonly known as a HDD (hard disk drive) or hard drive (HD) and formerly known as a fixed disk) is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to a device that drives (removable) media, such as a tape drive or (floppy) disk drive, while a hard disk contains fixed (non-removable) media. [1] However, in recent times, the hard disk has become more commonly known as the "hard drive." Image File history File links Hard_disk_platter_reflection. ... September 13 is the 256th day of the year (257th in leap years). ... Year 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ... Reynold Johnson (1906-1998) was an American inventor and computer pioneer. ... Image File history File links Download high resolution version (1024x683, 323 KB) Summary Alpha six, http://www. ... Image File history File links Download high resolution version (1024x683, 323 KB) Summary Alpha six, http://www. ... A hard disk platter is a component of a hard disk drive, which may have one or more hard disk platters. ... Non-volatile storage is a category of computer storage. ... Hard disk platter From Wikipedia, the free encyclopedia. ... In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ...


Hard disks were originally developed for use with computers. In the 21st century, applications for hard disks have expanded beyond computers to include digital video recorders, digital audio players, personal digital assistants, and digital cameras. In 2005 the first mobile phones to include hard disks were introduced by Samsung Group and Nokia. The need for large-scale, reliable storage, independent of a particular device, led to the introduction of configurations such as RAID, hardware such as network attached storage (NAS) devices, and systems such as storage area networks (SANs) for efficient access to large volumes of data. A BlueGene supercomputer cabinet. ... Foxtel IQ, a digital video recorder and a digital cable set-top box. ... Apple iPod, the most popular hard drive-based digital audio player An embedded hard drive-based player (Creative Zen Vision:M), one of the many alternatives for the iPod An MP3 CD player (Philips Expanium) Some mobile phones can be used as digital audio players, such as the Nokia 6233. ... palmOne Tungsten T5 Personal digital assistants (PDAs) are handheld computers that were originally designed as personal organizers, but became much more versatile over the years. ... This article or section does not cite its references or sources. ... The Samsung Group is a South Korean conglomerate (chaebol) composed of numerous businesses, including Samsung Electronics. ... Nokia Corporation (OMX: NOK1V, NYSE: NOK, FWB: NOA3) is currently the worlds largest manufacturer of mobile telephones, with a global market share of approximately 36% in Q4 of 2006. ... In computing, a redundant array of inexpensive disks, also later known as redundant array of independent disks (commonly abbreviated RAID) is a system which uses multiple hard drives to share or replicate data among the drives. ... Network-attached storage (NAS) systems are generally computing-storage devices that can be accessed over a computer network, rather than directly being connected to the computer (via a computer bus). ... In computing, a storage area network (SAN) is a network (referred to as a fabric) designed to attach computer storage devices such as disk array controllers, tape libraries and CD arrays to servers. ...

Contents

Technology

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

Hard disks record data by magnetizing a magnetic material in a pattern that represents the data. They read the data back by detecting the magnetization of the material. A typical hard disk design consists of a spindle which holds one or more flat circular disks called platters, onto which the data is recorded. The platters are made from a non-magnetic material, usually glass or aluminum, and are coated with a thin layer of magnetic material. Older disks used iron(III) oxide as the magnetic material, but current disks use a cobalt-based alloy. Image File history File links MagneticMedia. ... Image File history File links MagneticMedia. ... Frequency modulation (FM) is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave. ... Iron(III) oxide — also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust — is one of several oxide compounds of iron, and has paramagnetic properties. ... This article or section does not adequately cite its references or sources. ...


The platters are spun at very high speeds. Information is written to a platter as it rotates past mechanisms called read-and-write heads that fly very close 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 inside of a hard disk drive with the disk(s) and spindle motor hub removed. To the left of center is the actuator arm. A read-write head is at the end of the arm. In the middle the internal structure of the drive's spindle motor can be seen.
The inside of a hard disk drive with the disk(s) and spindle motor hub removed. To the left of center is the actuator arm. A read-write head is at the end of the arm. In the middle the internal structure of the drive's spindle motor can be seen.

The magnetic surface of each platter is divided into many small sub-micrometre-sized magnetic regions, each of which is used to encode a single binary unit of information. In today's hard disks each of these magnetic regions is composed of a few hundred magnetic grains. Each magnetic region forms a magnetic dipole which generates a highly localised magnetic field nearby. The write head magnetizes a magnetic region by generating a strong local magnetic field nearby. Early hard disks used the same inductor that was used to read the data as an electromagnet to create this field. Later versions of inductive heads included, metal in Gap (MIG) heads and thin film heads. In today's heads the read and write elements are separate but are 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[2]. Download high resolution version (1024x717, 141 KB)A dismantled 10GB Quantum Fireball hard drive Date: 28th July 2004 22:51 Camera: Canon DIGITAL IXUS II Exposure: 1/8 sec. ... Download high resolution version (1024x717, 141 KB)A dismantled 10GB Quantum Fireball hard drive Date: 28th July 2004 22:51 Camera: Canon DIGITAL IXUS II Exposure: 1/8 sec. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. ... This article is about the electromagnetic phenomenon. ... Current (I) flowing through a wire produces a magnetic field () around the wire. ... Thin films are material layers of about 1 µm thickness. ...


Hard disks have a mostly sealed enclosure that protects the disk internals from dust, condensation, and other sources of contamination. The hard disk's read-write heads fly on an air bearing which is a cushion of air only nanometers above the disk surface. The disk surface and the disk's internal environment must therefore be kept immaculate to prevent damage from fingerprints, hair, dust, smoke particles and such, given the sub-microscopic gap between the heads and disk. After just three years of use, dust has blocked this laptop heat sink, making the computer unusable Dust is a general name for minute solid particles with diameters less than 500 micrometers (otherwise, please see sand or granulates and, more generally, finely divided matter). ... Water vapor condensing over a cup of hot tea Condensation is the change in matter of a substance to a denser phase, such as a gas (or vapor) to a liquid. ... An air bearing is a bearing that literally consists of a layer of atmospheric air used as the working fluid for a fluid bearing. ... A nanometre (American spelling: nanometer) is 1. ...


Using rigid platters 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 access and transmit it faster. In 2007, a typical enterprise, i.e. workstation hard disk might store between 160 GB and 750 GB of data (as of local US market by December 2006), rotate at 7,200 to 10,000 revolutions per minute (RPM), and have a sequential media transfer rate of over 80 MB/s. The fastest enterprise hard disks spin at 15,000 RPM, and can achieve sequential media transfer speeds up to and beyond 110 MB/s.[3] Mobile, i.e., Laptop hard disks, which are physically smaller than their desktop and enterprise counterparts, tend to be slower and have less capacity. In the 1990's, most spun at 4,200 RPM[4]. In 2007 a typical mobile hard disk spins at 5,400 RPM and 7,200 RPM models are readily available for a slight price premium. A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ... Sun SPARCstation 1+, 25mhz RISC processor from early 1990s A workstation, such as a Unix workstation, RISC workstation or engineering workstation, is a high-end desktop or deskside microcomputer designed for technical applications. ... Revolutions per minute (abbreviated rpm, RPM, r/min, or min-1) is a unit of frequency, commonly used to measure rotational speed, in particular in the case of rotation around a fixed axis. ... A laptop computer, or simply laptop (also notebook computer or notebook), is a small mobile computer, which usually weighs 2. ...


Capacity

PC hard disk capacity (in GB). The plot is logarithmic, so the fit line corresponds to exponential growth.
PC hard disk capacity (in GB). The plot is logarithmic, so the fit line corresponds to exponential growth.

The exponential increases in disk space and data access speeds for hard disks has enabled the commercial viability of consumer products that require large storage capacities, such as the Apple iPod digital music player, the TiVo personal video recorder, and web-based email programs, like Google's Gmail.[5] Gmail goes so far as to display a simulation of a real-time counter showing the amount of storage space available to an account as it increases each second. Image File history File links Hard_drive_capacity_over_time. ... Image File history File links Hard_drive_capacity_over_time. ... Apple Macintoshes like the iMac Core Duo are personal computers. ... A gigabyte (symbol GB) is a unit of measurement in computers of one thousand million bytes (the same as one billion bytes in the short scale usage). ... A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself. ... In mathematics, a quantity that grows exponentially is one whose growth rate is always proportional to its current size. ... iPod (fifth generation) in Apple Universal Dock, iPod nano (second generation) and iPod shuffle (second generation) iPod is a brand of portable media players designed and marketed by Apple and launched in 2001. ... iPod Creative Zen Micro A digital audio player (DAP) is a device that stores, organizes and plays digital music files. ... TiVo (pronounced tee-voh, IPA: ) is a popular brand of digital video recorder (DVR) in the United States. ... A digital video recorder (DVR) is a device that records video to a digital storage medium in digital form. ... Google, Inc. ... Gmail, known as Google Mail in Germany and the United Kingdom, is a free Webmail and POP3 e-mail service provided by Google. ... Gmail, known as Google Mail in Germany and the United Kingdom, is a free Webmail and POP3 e-mail service provided by Google. ...


This is also gradually but significantly altering how programmers think; in many programming tasks there is a time-space tradeoff, so as space becomes cheaper and cheaper relative to CPU cycles the appropriate choice about time versus space changes. For instance in database work it is now common practice to store precomputed views, transitive closures, and the like on disk in order to speed up queries; 20 years ago such profligate use of disk space would have been impractical. In mathematics, the transitive closure of a binary relation R on a set X is the smallest transitive relation on X that contains R. For any relation R the transitive closure of R always exists. ...


A vice president of Seagate projects a future growth in disk density of 40% per year. [6] Access times have not kept up with throughput increases, which themselves have not kept up with growth in storage capacity. Seagate can refer to: Seagate Technology, a high tech manufacturer Seagate, Brooklyn, a community in Brooklyn, USA Seagate, Friends of, the nonprofit 501(c)(3) organization founded to preserve the historic winter retreat of Gwendolyn and Powel Crosley in Sarasota, Florida, USA Seagate, North Carolina, a community in North Carolina... In telecommunication, the term access time has the following meanings: In a telecommunication system, the elapsed time between the start of an access attempt and successful access. ...


The main way to decrease access time is to increase rotational speed, while the main way to increase throughput and storage capacity is to increase areal density. However, areal density is determined by two factors: recording density and track density. Track density measures how many tracks that can be packed into one area of space, while recording density measures the amount of data stored in a given physical length unit. Although higher track density can improve seek time, as disk head does not have to move as far to reach scattered data, improvement on transfer rate is not as important as increasing recording density. In the case of Seagate Barracuda 7200.10, only some versions have the extra recording density and throughput.[7]


Capacity measurements

Hard disk manufacturers specify disk capacity using the SI definition of the prefixes "mega," "giga," and "tera." This is largely for historical reasons. Disks with multi-million byte capacity have been used since 1956, long before there were standard binary prefixes. The International Electrotechnical Commission (IEC) only standardized binary prefixes in 1999. Many practitioners early on in the computer and semiconductor industries used the prefix kilo to describe 210 (1024) bits, bytes or words because 1024 is close to 1000. Similar usage has been applied to the prefixes mega, giga, tera, and even peta. Often this non-SI conforming usage is noted by a qualifier such as "1 kB = 1,024 bytes" but the qualifier is sometimes omitted, particularly in marketing literature. Manufacturing is the transformation of raw materials into finished goods for sale, or intermediate processes involving the production or finishing of semi-manufactures. ... An SI prefix is a prefix that can be applied to an SI unit to form a decimal multiple (supramultiple or submultiple). ... mega- (symbol M) is an SI prefix in the SI system of units denoting a factor of 106, i. ... Look up giga- in Wiktionary, the free dictionary. ... tera- (symbol: T) is a prefix in the SI system of units denoting 1012, or 1 000 000 000 000. ... In computing, binary prefixes can be used to quantify large numbers where powers of two are more useful than powers of ten. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... Kilo (symbol: k) is a prefix in the SI system denoting 103 or 1000. ... mega- (symbol M) is an SI prefix in the SI system of units denoting a factor of 106, i. ... Look up giga- in Wiktionary, the free dictionary. ... tera- (symbol: T) is a prefix in the SI system of units denoting 1012, or 1 000 000 000 000. ... In physics and mathematics, peta- (symbol: P) is a prefix in the SI (system of units) denoting 1015, or 1 000 000 000 000 000. ...


Operating systems, such as Microsoft Windows, frequently report capacity using the binary interpretation of the prefixes, which results in a discrepancy between the disk manufacturer's stated capacity and what the system reports. The difference becomes much more noticeable in the multi-gigabyte range. For example, Microsoft's Windows 2000 reports disk capacity both in decimal to 12 or more significant digits and with binary prefixes to 3 significant digits. Thus a disk specified by a disk manufacturer as a 30 GB disk might have its capacity reported by Windows 2000 both as "30,065,098,568 bytes" and "28.0 GB." The disk manufacturer used the SI definition of "giga," 109. However utilities provided by Windows define a gigabyte as 230, or 1,073,741,824, bytes, so the reported capacity of the disk will be closer to 28.0 GB. For this reason, many utilities that report capacity have begun to use the aforementioned IEC standard binary prefixes (e.g. KiB, MiB, GiB) since their definitions are unambiguous. Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ... Cover of brochure The International System of Units. ... A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to... A mebibyte (a contraction of mega binary byte) is a unit of information or computer storage, abbreviated MiB. 1 MiB = 220 bytes = 1,048,576 bytes = 1,024 kibibytes The mebibyte is closely related to the megabyte (MB), which can either be a synonym for mebibyte, or refer to 106... A gibibyte is a unit of information or computer storage. ...


Some people mistakenly attribute the discrepancy in reported and specified capacities to reserved space used for file system and partition accounting information. However, for large (several GiB) filesystems, this data rarely occupies more than a few MiB, and therefore cannot possibly account for the apparent "loss" of tens of GBs.


The capacity of a hard disk 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). However, the cylinder, head, sector values are not accurate for drives using zone bit recording, or address translation. On ATA drives bigger than 8 gibibytes, the values are set to 16383 cylinder, 16 heads, 63 sectors for compatibility with older operating systems. Zone Bit Recording (ZBR) is used by disk drives to store more sectors per track on outer tracks than on inner tracks. ... AT Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers, maintained by X3/INCITS committee T13. ...


History

Main article: History of hard disks
IBM 62PC "Piccolo" HDD, circa 1979 - an early 8" disk
IBM 62PC "Piccolo" HDD, circa 1979 - an early 8" disk
A 2.5" hard disk for laptops, circa 2000
A 2.5" hard disk for laptops, circa 2000

For many years, hard disks were large, cumbersome devices, more suited to use in the protected environment of a data center or large office than in a harsh industrial environment (due to their delicacy), or small office or home (due to their size and power consumption). Before the early 1980s, most hard disks had 8-inch (20 cm) or 14-inch (35 cm) platters, required an equipment rack or a large amount of floor space (especially the large removable-media disks, which were often referred to as "washing machines"), and in many cases needed high-current or even three-phase power hookups due to the large motors they used. Because of this, hard disks were not commonly used with microcomputers until after 1980, when Seagate Technology introduced the ST-506, the first 5.25-inch hard disk, with a capacity of 5 megabytes. In fact, in its factory configuration, the original IBM PC (IBM 5150) was not equipped with a hard disk. The history of hard disks began in 1955 with the IBM 305 computer. ... Image File history File links Download high resolution version (1606x1292, 380 KB) Summary Old IBM Hard Disk Drive. ... Image File history File links Download high resolution version (1606x1292, 380 KB) Summary Old IBM Hard Disk Drive. ... Image File history File linksMetadata Download high-resolution version (2560x1920, 1950 KB) Copyright © 2007 David Monniaux File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Hard disk Metadata This file contains additional information, probably added from the digital camera... Image File history File linksMetadata Download high-resolution version (2560x1920, 1950 KB) Copyright © 2007 David Monniaux File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Hard disk Metadata This file contains additional information, probably added from the digital camera... Front-loading washing machine. ... Seagate Technology (NYSE: STX) is a major American manufacturer of hard drives, founded in 1979 and based in Scotts Valley, California. ... The ST-506 was the first hard disk intended for use specifically on microcomputers, introduced in 1980 by Seagate Technology. ... IBM PC (IBM 5150) with keyboard and green screen monochrome monitor (IBM 5151), running MS-DOS 5. ...


Most microcomputer hard disks in the early 1980s were not sold under their manufacturer's names, but by OEMs as part of larger peripherals (such as the Corvus Disk System and the Apple ProFile). The IBM PC/XT had an internal hard disk, however, and this started a trend toward buying "bare" disks (often by mail order) and installing them directly into a system. Hard disk makers started marketing to end users as well as OEMs, and by the mid-1990s, hard disks had become available on retail store shelves. Original equipment manufacturer, or OEM, is a term that refers to a situation in which one company purchases a manufactured product from another company and resells the product as its own, usually as a part of a larger product the original company is selling. ... Apple Lisa with a ProFile hard drive. ... Mail order is a term which describes the buying of goods or services by mail delivery. ...


While internal disks became the system of choice on PCs, external hard disks remained popular for much longer on the Apple Macintosh and other platforms. Every Mac made between 1986 and 1998 has a SCSI port on the back, making external expansion easy. External SCSI disks were also popular with older microcomputers such as the Apple II series, and were also used extensively in servers, a usage which is still popular today. The appearance in the late 1990s of high-speed external interfaces such as USB and FireWire has made external disk systems popular among PC users once again, especially for users who move large amounts of data between two or more areas, and most hard disk makers now make their disks available in external cases. The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... This article or section does not adequately cite its references or sources. ... The Apple II was one of the most popular personal computers of the 1980s. ... This article or section does not cite its references or sources. ... Universal Serial Bus (USB) is a serial bus standard to interface devices. ... The 6-pin and 4-pin FireWire Connectors FireWire is Apple Inc. ...


Hard disk characteristics

5.25" MFM 110 MB hard disk (2.5" ATA 6495 MB hard disk, US & UK pennies for comparison)
5.25" MFM 110 MB hard disk (2.5" ATA 6495 MB hard disk, US & UK pennies for comparison)
  • Capacity, usually quoted in gigabytes. (older hard disks used to quote their smaller capacities in megabytes)
  • Physical size, usually quoted in inches:
    • Almost all hard disks today are of either the 3.5" or 2.5" varieties, used in desktops and laptops, respectively. 2.5" disks are usually slower and have less capacity, but use less power and are more tolerant of movement. However, as of early 2007, manufacturers have started selling SATA and SAS 2.5" drives for use in servers and desktops.
    • An increasingly common size is the 1.8" ATA-7 LIF form factor used inside digital audio players and subnotebooks, which provide up to 100GB storage capacity at low power consumption and are highly shock-resistant. A previous 1.8" hard disk standard exists, for 2-5GB sized disks that fit directly into PCMCIA or Cardbus expansion slots. From these, the smaller 1" form factor was evolved, which is designed to fit the dimensions of CF Type II, which is also usually used as storage for portable devices including digital cameras. 1" was a de facto form factor led by IBM's Microdrive, but is now generically called 1" due to other manufacturers producing similar products. There is also a 0.85" form factor produced by Toshiba for use in mobile phones and similar applications, including SD/MMC slot compatible hard disks optimized for video storage on 4G handsets.
    • The size designations are more nomenclature than descriptive: for example, a 3.5" drive is named for the size of the floppy disk whose drive bay size it was originally designed to occupy; the drive itself is actually wider.
    • The physical dimensions of the most common hard drive bays are as follows
Standard Name Width
5.25" 5.75"
3.5" 4"
2.5" 2.75"
1.8" (PCMCIA) 54 millimeters
1.8" (ATA-7 LIF) 2.12"
Standard Name Height
Full Height 3.25"
Half Height 1.625"
Slim Height / Low Profile 1"
Ultra Low Profile 0.75"
0.67"
0.49"
0.37"
  • Number of I/O operations per second:
  • Power consumption (especially important in battery-powered laptops).
  • audible noise in dBA (although many still report it in bels, not decibels).
  • G-shock rating (surprisingly high in modern disks).
  • Transfer Rate:
    • Inner Zone: from 44.2 MB/s to 74.5 MB/s.
    • Outer Zone: from 74.0 MB/s to 111.4 MB/s.
  • Random access time: from 5 ms to 15 ms.

Image File history File linksMetadata 5. ... Image File history File linksMetadata 5. ... A gigabyte (derived from the SI prefix giga-) is a unit of information or computer storage equal to one billion (short scale, meaning a thousand million) bytes. ... This article is about a unit of data measurement. ... An inch (plural: inches; symbol or abbreviation: in or, sometimes, ″ - a double prime) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... Apple iPod, the most popular hard drive-based digital audio player An embedded hard drive-based player (Creative Zen Vision:M), one of the many alternatives for the iPod An MP3 CD player (Philips Expanium) Some mobile phones can be used as digital audio players, such as the Nokia 6233. ... Sony VAIO model C1 subnotebook A subnotebook (also known as a kneetop or an ultraportable) is an extremely small and lightweight portable computer, with all features of a standard laptop computer and running all its applications. ... Portable Computer Cards (PC cards) are interchangeable peripherals designed to be inserted into laptop computers in order to enable extra hardware functions. ... The PCMCIA is the Personal Computer Memory Card International Association, an industry trade association that creates standards for notebook computer peripheral devices. ... CompactFlash (CF) was originally a type of data storage device, used in portable electronic devices. ... This article or section does not cite its references or sources. ... De facto is a Latin expression that means in fact or in practice. It is commonly used as opposed to de jure (meaning by law) when referring to matters of law or governance or technique (such as standards), that are found in the common experience as created or developed without... International Business Machines Corporation (known as IBM or Big Blue; NYSE: IBM) is a multinational computer technology corporation headquartered in Armonk, New York, USA. The company is one of the few information technology companies with a continuous history dating back to the 19th century. ... For other uses, see Microdrive (disambiguation). ... This article does not adequately cite its references or sources. ... MMC may stand for: In computing and electronics: MultiMediaCard, a solid state disk or flash memory data storage device Microsoft Management Console, a framework for system administration tools in modern Microsoft Windows operating systems Multi-Memory Controller, a special microchip in Nintendo Entertainment System Game Paks MIDI Machine Control, part... This article is about the mobile phone standard. ... In computer science, random access is the ability to access a random element of a group in equal time. ... In computer science sequential access means that a group of elements (e. ... In electrical engineering, power consumption refers to the electrical energy over time that must be supplied to an electrical device to maintain its operation. ... DBA may mean: // Decibels audible Diamond-Blackfan anemia Dibenzylideneacetone .dba format, a calendar format for Palm Desktop Doctor of Business Administration, an academic doctoral degree dba, a low-cost German airline The Dallas Bar Association for lawyers in Texas, USA A database administrator (or analyst) A-weighted decibels (dBA), in...

Integrity

An IBM hard disk head suspended above the disk platter.
An IBM hard disk head suspended above the disk platter.

The hard disk's spindle system relies on air pressure inside the enclosure to support the heads at their proper flying height while the disk is in motion. A hard disk requires 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 1/2 mm in diameter), usually with a carbon filter on the inside (the breather filter, see below). If the air pressure is too low, there will not be enough lift for the flying head, the head will not be at the proper height, 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 10,000 feet (3,000 m). This does not apply to pressurized enclosures, like an airplane pressurized cabin. Modern disks include temperature sensors and adjust their operation to the operating environment. Image File history File links Download high-resolution version (1024x725, 286 KB) This is a side view of the read head of an IBM hard disk, circa 2002. ... Image File history File links Download high-resolution version (1024x725, 286 KB) This is a side view of the read head of an IBM hard disk, circa 2002. ... An Airbus A380, currently the worlds largest passenger airliner An aircraft is any vehicle or craft capable of atmospheric flight. ... Cabin pressurization is the active pumping of air into the cabin of an aircraft to increase the air pressure within the cabin. ...


Very high humidity for extended periods can cause accelerated wear of the heads and platters by corrosion. If the disk uses "Contact Start/Stop" (CSS) technology to park its heads on the platters when not operating, increased humidity can also lead to increased stiction (the tendency for the heads to stick to the platter surface). This can cause physical damage to the platter and spindle motor and can also lead to head crash. Breather holes can be seen on all disks — they usually have a warning sticker next to them, informing the user not to cover the holes. The air inside the operating disk 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. This article should be split into multiple articles accessible from a disambiguation page. ... A head crash occurs when the read-write head of a hard disk drive touches its rotating platter. ...

Close-up of a hard disk head suspended above the disk platter together with its mirror image in the smooth surface of the magnetic platter.
Close-up of a hard disk head suspended above the disk platter together with its mirror image in the smooth surface of the magnetic platter.

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. For giant magnetoresistive (GMR) heads in particular, a minor head crash from contamination (that does not remove the magnetic surface of the disk) will still result 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). Head crashes can be caused by electronic failure, a sudden power failure, physical shock, wear and tear, corrosion, or poorly manufactured platters and heads. In most desktop and server disks, when powering down, the heads are moved to a landing zone, an area of the platter usually near its inner diameter (ID), where no data is stored. This area is called the CSS (Contact Start/Stop) zone. However, especially in old models, sudden power interruptions or a power supply failure can sometimes result in the device shutting down with the heads in the data zone, which increases the risk of data loss. In fact, it used to be procedure to "park" the hard disk before shutting down your computer. Newer disks are designed such that either a spring (at first) or (more recently) rotational inertia in the platters is used to safely park the heads in the case of unexpected power loss. Image File history File linksMetadata Download high resolution version (1698x1542, 228 KB) Summary A hard disk drive head resting on the disk platter. ... Image File history File linksMetadata Download high resolution version (1698x1542, 228 KB) Summary A hard disk drive head resting on the disk platter. ... A head crash occurs when the read-write head of a hard disk drive touches its rotating platter. ... Founding results of Fert The Giant Magnetoresistance Effect (GMR) is a quantum mechanical effect observed in thin film structures composed of alternating ferromagnetic and nonmagnetic metal layers. ...


The hard disk'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. Modern disk firmware is capable of scheduling reads and writes efficiently on the platter surfaces and remapping sectors of the media which have failed. Also, most major hard disk and motherboard vendors now support self-monitoring, analysis, and reporting technology (S.M.A.R.T.), which attempt to alert users to impending failures. The disk controller (or hard disk controller) is the circuit which allows the CPU to communicate with a hard disk, floppy disk or other kind of disk drive. ... Self-Monitoring, Analysis, and Reporting Technology, or S.M.A.R.T., is a monitoring system for computer hard disks to detect and report on various indicators of reliability, in the hope of anticipating failures. ...


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 can lead to the loss of data. While it may be possible to recover lost information, it is normally an extremely costly procedure, and it is not possible to guarantee success in the attempt. A 2007 study published by Google suggested very little correlation between failure rates and either high temperature or activity level.[8] 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.[8] S.M.A.R.T. parameters alone may not be useful for predicting individual drive failures.[8] Google, Inc. ...


Landing zones

Microphotograph of a hard disk head. The size of the front face (which is the "trailing face" of the slider) is about 0.3 mm × 1.0 mm. The (not visible) bottom face of the slider is about 1.0 mm × 1.25 mm (so called "nano" size) and faces the platter. One functional part of the head is the round, orange structure in the middle - the lithographically defined copper coil of the write transducer. Also note the electric connections by wires bonded to gold-plated pads.
Microphotograph of a hard disk head. The size of the front face (which is the "trailing face" of the slider) is about 0.3 mm × 1.0 mm. The (not visible) bottom face of the slider is about 1.0 mm × 1.25 mm (so called "nano" size) and faces the platter. One functional part of the head is the round, orange structure in the middle - the lithographically defined copper coil of the write transducer. Also note the electric connections by wires bonded to gold-plated pads.

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 reliably survive a number of landings and takeoffs from the media surface, though wear and tear on these microscopic components eventually takes its toll. The heads typically land in a "landing zone" that does not contain user data. 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 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. [1] This means that no failures attributed to the head-platter interface were seen before at least 50,000 start-stop cycles during testing. Image File history File links Download high resolution version (890x598, 59 KB) Summary Microphotograph of a r/w head from a hard disk. ... Image File history File links Download high resolution version (890x598, 59 KB) Summary Microphotograph of a r/w head from a hard disk. ... A micrograph is a photograph or similar image taken through a microscope or similar device to show a magnified image of an item. ...


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 (2006). In most mobile applications, the heads are lifted off the platters onto plastic "ramps" near the outer disk edge, thus eliminating the risks of wear and stiction altogether and greatly improving non-operating shock performance. All HDD's use one of these two technologies. Each has a list of advantages and drawbacks in terms of loss of storage space, relative difficulty of mechanical tolerance control, cost of implementation, etc.


IBM 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 motion sensor in the Thinkpad, internal hard disk heads automatically unload themselves into the parking zone to reduce the risk of any potential data loss or scratches made. Apple later also utilized this technology in their Powerbook, iBook, MacBook Pro, and MacBook line, known as the Sudden Motion Sensor. International Business Machines Corporation (known as IBM or Big Blue; NYSE: IBM) is a multinational computer technology corporation headquartered in Armonk, New York, USA. The company is one of the few information technology companies with a continuous history dating back to the 19th century. ... This article or section does not cite its references or sources. ... The Sudden Motion Sensor is a patent-pending data protection feature introduced by Apple Computer into its refreshed PowerBook and iBook lines on January 1, 2005 and July 26, 2005 respectively. ...


Access and interfaces

Hard disk drives are accessed over one of a number of bus types, including ATA (IDE, EIDE), Serial ATA (SATA), SCSI, SAS, and Fibre Channel. Bridge circuitry is sometimes used to connect hard disk drives to busses that they cannot communicate with natively, such as IEEE 1394 and USB. ATA cables: 40 wire ribbon cable top, 80 wire ribbon cable bottom Advanced Technology Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers. ... This article or section does not adequately cite its references or sources. ... This article or section does not adequately cite its references or sources. ... In computer hardware, Serial Attached SCSI (SAS) is a computer bus technology primarily designed for transfer of data to and from devices like hard disk, cd-rom and so on. ... This article or section does not adequately cite its references or sources. ... A 6-Pin Firewire 400 connector FireWire (also known as i. ... Universal Serial Bus (USB) is a serial bus standard to interface devices. ...


Back in the days of the ST-506 interface, the data encoding scheme 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 on, controllers using 2,7 RLL (or just "RLL") encoding increased the transfer rate by fifty percent, to 7.5 megabits per second; it also increased disk capacity by fifty percent. The ST-506 was the first hard disk intended for use specifically on microcomputers, introduced in 1980 by Seagate Technology. ... The word encoding has a number of meanings. ... Modified Frequency Modulation, commonly MFM, is a line code used by most floppy disk formats, notably by most CP/M machines, as well as PCs running DOS. MFM is a modification to the original FM (frequency modulation) scheme for encoding data on single-density floppy disks. ... The Megabit is a unit of information storage, abbreviated Mbit or sometimes Mb. ... Run Length Limited, commonly RLL, is the most popular scheme for encoding data on hard disks. ...


Many ST-506 interface disk drives were only specified by the manufacturer to run at the lower MFM data rate, while other models (usually more expensive versions of the same basic disk drive) were specified to run at the higher RLL data rate. In some cases, a disk drive had sufficient margin to allow the MFM specified model to run at the faster RLL data rate; however, this was often unreliable and was not recommended. (An RLL-certified disk drive could run on a MFM controller, but with 1/3 less data capacity and speed.)


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. Enhanced Small Disk Interface (ESDI) was a disc interface designed by Maxtor Corporation in the early 1980s to be a follow-on to the ST-506 interface. ...


SCSI originally had just one speed, 5 MHz (for a maximum data rate of 5 megabytes per second), 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 IBM PC compatibles and early Apple Macintoshes. This article or section does not cite its references or sources. ... The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ...


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 in a master/slave setup (two disks on the same cable). This was mostly remedied by the mid-1990s, when ATA's specification was standardised 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). ATA cables: 40 wire ribbon cable top, 80 wire ribbon cable bottom Advanced Technology Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers. ...


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) hard disks 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. The elementary meaning of daisy chain is a garland created from the daisy flower, generally as a childrens game. ...


Disk families used in personal computers

Notable disk families include:

  • Bit Serial Interfaces - These families connected to a hard disk controller with three cables, one for data, one for control and one for power. The hard disk controller provided significant functions such as serial to parallel conversion, data separation and track formating, and required matching to the drive in order to assure reliability.
    • ST506 used MFM (Modified Frequency Modulation) for the data encoding method.
    • ST412 was available in either MFM or RLL (Run Length Limited) variants.
    • ESDI (Enhanced Small Disk Interface) was an interface developed by Maxtor to allow faster communication between the PC and the disk than MFM or RLL.
  • Word Serial Interfaces These families connect to a host bus adapter (today typically integrated into the "North Bridge") with two cables, one for data/control and one for power. The earliest versions of these interfaces typically had a 16 bit parallel data transfer to/from the drive and there are 8 and 32 bit variants. Modern versions 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 hard disk controller.
    • Integrated Drive Electronics (IDE) was later renamed to ATA, and then PATA. The name comes from the way early families had the hard disk controller external to the disk. Moving the hard disk controller from the interface card to the disk helped to standardize interfaces, including reducing the cost and complexity. In 2005/2006 parlance, the 40 pin IDE/ATA is called "PATA" or parallel ATA, which means that there are 16 bits of data transferred in parallel at a time on the data cable. The data cable was originally 40 conductor, but UDMA modes from the later disks requires using an 80 conductor cable (note that the 80 conductor cable still uses a 40 position connector.) The interface changed from 40 pins to 39 pin. The missing pin acts as a key to prevent incorrect insertion of the connector, 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 DMA to transfer data between the disk and the computer, an improvement later adopted by the official ATA standards. DMA is used to transfer data without the CPU or program being responsible to transfer every word. That leaves the CPU/program/operating system to do other tasks while the data transfer occurs.
    • SCSI (Small Computer System Interface) was an early competitor with ESDI, originally named SASI for Shugart Associates. SCSI disks were standard on servers, workstations, 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 data transmission, but server class SCSI could use differential transmission, and then Fibre Channel (FC) interface, and then more specifically the Fibre Channel Arbitrated Loop (FC-AL), connected SCSI hard disks using fibre optics. FC-AL is the cornerstone of storage area networks, although other protocols like iSCSI and ATA over Ethernet have been developed as well.
    • SATA (Serial ATA). 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. The same differential signaling system is used in RS485, LocalTalk, USB, Firewire, and differential SCSI.
    • SAS (Serial Attached SCSI). 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 serial communication instead of the parallel method found in traditional SCSI devices but still uses SCSI commands for interacting with SAS
Acronym Meaning Description
SASI Shugart Associates System Interface Predecessor to SCSI
SCSI Small Computer System Interface Bus oriented that handles concurrent operations.
ST-506 Seagate interface
ST-412 Seagate interface (minor improvement over ST-506)
ESDI Enhanced Small Disk Interface Faster and more integrated than ST-412/506, but still backwards compatible
ATA Advanced Technology Attachment Successor to ST-412/506/ESDI by integrating the disk controller completely onto the device. Incapable of concurrent operations.

Modified Frequency Modulation, commonly MFM, is a line code used by most floppy disk formats, notably by most CP/M machines, as well as PCs running DOS. MFM is a modification to the original FM (frequency modulation) scheme for encoding data on single-density floppy disks. ... Run Length Limited codes, or RLL codes are widely used in hard disk drives (and notably digital optical discs, such as CD, DVD and BluRay disc) to prevent long stretches of no transitions, and therefore decoding uncertainty, from creeping in. ... Enhanced Small Disk Interface (ESDI) was a disc interface designed by Maxtor Corporation in the early 1980s to be a follow-on to the ST-506 interface. ... ATA cables: 40 wire ribbon cable top, 80 wire ribbon cable bottom Advanced Technology Attachment (ATA), is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers. ... Direct memory access (DMA) is a feature of modern computers, that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit. ... This article or section does not adequately cite its references or sources. ... The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... This article or section does not adequately cite its references or sources. ... Arbitrated Loop also known as FC-AL is a Fibre Channel topology that requires no fibre channel switches. ... In computing, a storage area network (SAN) is a network (referred to as a fabric) designed to attach computer storage devices such as disk array controllers, tape libraries and CD arrays to servers. ... . The initial letter is shown capitalized due to technical restrictions. ... ATA over Ethernet (AoE) is a network protocol developed by Coraid, Inc. ... This article or section does not adequately cite its references or sources. ... EIA-422 (formerly RS-422) is a serial data communication protocol which specifies 4 wire, full-duplex, differential line, multi-drop communications. ... It has been suggested that this article or section be merged into Low voltage differential signaling. ... EIA-485 (formerly RS-485 or RS485) is an OSI Model physical layer electrical specification of a two-wire, half-duplex, multipoint serial connection. ... LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. ... Note: USB may also mean upper sideband in radio. ... The 6-pin and 4-pin FireWire Connectors FireWire is Apple Inc. ... This article or section does not adequately cite its references or sources. ... In computer hardware, Serial Attached SCSI (SAS) is a computer bus technology primarily designed for transfer of data to and from devices like hard disk, cd-rom and so on. ... It has been suggested that this article or section be merged with Backronym and Apronym (Discuss) Acronyms and initialisms are abbreviations, such as NATO, laser, and ABC, written as the initial letter or letters of words, and pronounced on the basis of this abbreviated written form. ... SCSI stands for Small Computer System Interface, and is a standard interface for transferring data between devices on a computer bus. ... This article or section does not adequately cite its references or sources. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ... Parallel programming (also concurrent programming), is a computer programming technique that provides for the execution of operations concurrently, either within a single computer, or across a number of systems. ... The ST-506 was the first hard disk intended for use specifically on microcomputers, introduced in 1980 by Seagate Technology. ... This does not cite its references or sources. ... Enhanced Small Disk Interface (ESDI) was a disc interface designed by Maxtor Corporation in the early 1980s to be a follow-on to the ST-506 interface. ... ATA cables: 40 wire ribbon cable top, 80 wire ribbon cable bottom Advanced Technology Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers. ... A successor function is the label in the literature for what is actually an operation. ...

Manufacturers

Seagate 3.5 inch 30 GB hard disk.
Seagate 3.5 inch 30 GB hard disk.

As of 2007, over 98% of the world's hard disks are manufactured by just a handful of large firms: Seagate, Western Digital, Samsung, and Hitachi which owns the former disk manufacturing division of IBM. Fujitsu continues to make mobile- and server-class disks but exited the desktop-class market in 2001. Toshiba is a major manufacturer of 2.5-inch and 1.8-inch notebook disks. Image File history File links Seagate_Hard_Disk. ... Image File history File links Seagate_Hard_Disk. ... Seagate Technology (NYSE: STX) is a major American manufacturer of hard drives, founded in 1979 and based in Scotts Valley, California. ... Seagate Technology (NYSE: STX) is a major American manufacturer of hard drives, founded in 1979 and based in Scotts Valley, California. ... Western Digital Corporation (NYSE: WDC) (often abbreviated to WD) is a manufacturer of a large proportion of the worlds hard disks, and has a long history in the electronics industry as an IC maker and a storage products company. ... Samsung Group is one of the largest South Korean business groupings. ... Hitachi Ltd. ... International Business Machines Corporation (IBM, or colloquially, Big Blue) (NYSE: IBM) (incorporated June 15, 1911, in operation since 1888) is headquartered in Armonk, New York, USA. The company manufactures and sells computer hardware, software, and services. ... For the district in Saga, Japan, see Fujitsu, Saga. ... This article does not adequately cite its references or sources. ...


Dozens of former hard disk manufacturers have gone out of business, merged, or closed their hard disk divisions; as capacities and demand for products increased, profits became hard to find, and there were shakeouts 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.[9] CMI's reputation never recovered, and they exited the hard disk business in 1987. Another notable failure was MiniScribe, who went bankrupt in 1990 after it was found that they had "cooked the books" 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 hard disks in India using a second hand factory.[citation needed] 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 hard disks. Computer Memories Inc. ... MiniScribe was a manufacturer of disk storage products, founded in Longmont, Colorado in 1980. ... Kalok was a hard disk drive manufacturer which went bankrupt in 1994. ... Micropolis Corporation was a SCSI hard drive manufacturing company located in Chatsworth, California. ... JT Storage (also known as JTS) was a maker of inexpensive IDE hard drives for personal computers based in San Jose, California. ...

  • 1988: Tandon sold its disk manufacturing division to Western Digital (WDC), which was then a well-known controller designer.
  • 1989: Seagate Technology bought Control Data's high-end disk business, as part of CDC's exit from hardware manufacturing.
  • 1990: Maxtor buys MiniScribe out of bankruptcy, making it the core of its low-end disk division.
  • 1994: Quantum bought DEC's storage division, giving it a high-end disk range to go with its more consumer-oriented ProDrive range, as well as the DLT tape drive range.
  • 1995, Conner Peripherals, which was founded by one of Seagate Technology's co-founders along with personnel from MiniScribe, announces a merger with Seagate, which was completed in early 1996.
  • 1996: JTS merges with Atari, allowing JTS to bring its disk range into production. Atari was sold to Hasbro in 1998, while JTS itself went bankrupt in 1999.
  • 2000: Quantum sells its disk division to Maxtor to concentrate on tape drives and backup equipment.
  • 2003: Following the controversy over mass failures of its Deskstar 75GXP range, hard disk pioneer IBM sold the majority of its disk division to Hitachi, who renamed it Hitachi Global Storage Technologies (HGST).
  • December 21, 2005: Seagate and Maxtor announced an agreement under which Seagate would acquire Maxtor in an all stock transaction valued at $1.9B. The acquisition was approved by the appropriate regulatory bodies, and closed on May 19, 2006.

Seagate Technology (NYSE: STX) is a major American manufacturer of hard drives, founded in 1979 and based in Scotts Valley, California. ... Control Data Corporation, or CDC, was one of the pioneering supercomputer firms. ... MiniScribe was a manufacturer of disk storage products, founded in Longmont, Colorado in 1980. ... Quantum Corporation is a manufacturer of tape drive products, based in San Jose, California. ... The DEC logo Digital Equipment Corporation was a pioneering American company in the computer industry. ... A Super DLT I tape cartridge Digital Linear Tape (DLT) is considered a de facto standard for magnetic tape technology used for computer data storage. ... Conner Peripherals was a company that manufactured hard drives for personal computers. ... This article or section does not cite its references or sources. ... Hasbro (NYSE: HAS) is an American toy and game company. ... DDS tape drive. ... In information technology, backup refers to the copying of data so that these additional copies may be restored after a data loss event. ... The Deskstar is a computer hard drive. ... Seagate can refer to: Seagate Technology, a high tech manufacturer Seagate, Brooklyn, a community in Brooklyn, USA Seagate, Friends of, the nonprofit 501(c)(3) organization founded to preserve the historic winter retreat of Gwendolyn and Powel Crosley in Sarasota, Florida, USA Seagate, North Carolina, a community in North Carolina... Maxtor Corporation (NYSE: MXO) was (as of December 2005) the worlds third-largest manufacturer of computer hard disk drives, before its acquisition by Seagate in 2006. ...

References

  1. ^ http://computer.howstuffworks.com/hard-disk1.htm
  2. ^ http://www.hitachigst.com/hdd/technolo/gmr/gmr.htm
  3. ^ http://anandtech.com/storage/showdoc.aspx?i=2922&p=1 Review of Western Digital's fastest Hard Disk as of February 2007
  4. ^ The 1999 Disk/Trend Hard Disk Drive Report lists 81 mobile hard disk having rotational speeds ranging from 3,634 to 4,900 RPM with 44 models operating at 4200RPM
  5. ^ Walter, Chip. "Kryder's Law", Scientific American, Verlagsgruppe Georg von Holtzbrinck GmbH, 25 July 2005. Retrieved on 2006-10-29.
  6. ^ http://www.hardwarezone.com/articles/view.php?cid=1&id=1805&pg=2
  7. ^ 500GB SATA drives reviews
  8. ^ a b c Barroso, L.A., et al. Failure Trends in a Large Disk Drive Population. February 2007.
  9. ^ 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 MSDOS 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"). MSDOS 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

July 25 is the 206th day (207th in leap years) of the year in the Gregorian calendar, with 159 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... October 29 is the 302nd day of the year (303rd in leap years) in the Gregorian calendar. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ...

See also

To meet Wikipedias quality standards, this article may require cleanup. ... Sequoia view is a free program for visualising hard disk usage by squares. ... The history of hard disks began in 1955 with the IBM 305 computer. ... Magnetic disk storage is a critical component of the computer revolution. ... In computing, a file system (often also written as filesystem) is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. ... A hybrid drive is a new type of large-buffer computer hard drive, currently in joint development by Samsung and Microsoft. ... AT Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers, maintained by X3/INCITS committee T13. ... Native Command Queuing (NCQ) is a technology designed to increase performance of SATA hard disks by allowing the individual hard disk to receive more than one I/O request at a time and dynamically change the order in which they are applied. ... In data storage, Partial Response Maximum Likelihood (PRML) is a method for converting the weak analog signal from the head of a magnetic disk drive into a digital signal. ... In computing, a redundant array of inexpensive disks, also later known as redundant array of independent disks (commonly abbreviated RAID) is a system which uses multiple hard drives to share or replicate data among the drives. ... The RK05 was a moving head magnetic disk drive manufactured by the Digital Equipment Corporation of Maynard, Massachusetts. ... This article or section does not adequately cite its references or sources. ... This article or section does not adequately cite its references or sources. ... Self-Monitoring, Analysis, and Reporting Technology, or S.M.A.R.T., is a monitoring system for computer hard disks to detect and report on various indicators of reliability, in the hope of anticipating failures. ... This article or section does not cite its references or sources. ... Superparamagnetism is a phenomenon by which magnetic materials may exhibit a behavior similar to paramagnetism even when at temperatures below the Curie or the Néel temperature. ...

External links

Wikimedia Commons has media related to:
Hard disk
  • The Hard Disk That Changed The World
  • TechEncyclopedia about Hard Disks
  • Hard disk interfaces pinouts
  • How Hard Disks Work
  • Digest 2005 - State of the art hard disk drives in 2005
  • War of the Disks: Hard Disk Drives vs. Flash Solid State Disks Despatches from the magneto / flash wars
  • Storage Review Reference Guide
  • PC Doctor takes you inside a hard drive
  • Disk Failures report by Google Labs

  Results from FactBites:
 
Hard disk - Wikipedia, the free encyclopedia (6551 words)
Hard disks are also found in network attached storage (NAS) devices, but for large volumes of data may be most efficiently used in a storage area network (SAN).
For many years, hard disks were large, cumbersome devices, more suited to use in the protected environment of a data center or large office than in a harsh industrial environment (due to their delicacy), or small office or home (due to their size and power consumption).
Most microcomputer hard disk drives in the early 1980s were not sold under their manufacturer's names, but by OEMs as part of larger peripherals (such as the Corvus Disk System and the Apple ProFile).
Hard disk recorder - Wikipedia, the free encyclopedia (518 words)
A hard disk recorder is a type of recording system that utilizes a high-capacity hard disk to record digital audio or digital video.
Hard disk recording systems represent an alternative to more traditional reel-to-reel tape or cassette multitrack systems, and provide editing capabilities unavailable to tape recorders.
Hard disk recorders are often combined with a digital mixing console and are an inherent part of a digital audio workstation.
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