58-550: The ProFile (codenamed Pippin ) is the first hard disk drive produced by Apple Computer , initially for use with the Apple III . The original model had a formatted capacity of 5 MB and connected to a special interface card that plugged into an Apple III slot. In 1983, Apple offered a ProFile interface card for the Apple II , with software support for Apple ProDOS and Apple Pascal . Additionally, in 1983, Apple introduced
116-684: A spindle that holds flat circular disks, called platters , which hold the recorded data. The platters are made from a non-magnetic material, usually aluminum alloy , glass , or ceramic . They are coated with a shallow layer of magnetic material typically 10–20 nm in depth, with an outer layer of carbon for protection. For reference, a standard piece of copy paper is 0.07–0.18 mm (70,000–180,000 nm) thick. The platters in contemporary HDDs are spun at speeds varying from 4200 rpm in energy-efficient portable devices, to 15,000 rpm for high-performance servers. The first HDDs spun at 1,200 rpm and, for many years, 3,600 rpm
174-522: A stepper motor . Early hard disk drives wrote data at some constant bits per second, resulting in all tracks having the same amount of data per track, but modern drives (since the 1990s) use zone bit recording , increasing the write speed from inner to outer zone and thereby storing more data per track in the outer zones. In modern drives, the small size of the magnetic regions creates the danger that their magnetic state might be lost because of thermal effects — thermally induced magnetic instability which
232-416: A "stopgap" technology between PMR and Seagate's intended successor heat-assisted magnetic recording (HAMR). SMR utilises overlapping tracks for increased data density, at the cost of design complexity and lower data access speeds (particularly write speeds and random access 4k speeds). By contrast, HGST (now part of Western Digital ) focused on developing ways to seal helium -filled drives instead of
290-582: A Field Generation Layer (FGL) and a Spin Injection Layer (SIL), and the FGL produces a magnetic field using spin-polarised electrons originating in the SIL, which is a form of spin torque energy. A typical HDD has two electric motors: a spindle motor that spins the disks and an actuator (motor) that positions the read/write head assembly across the spinning disks. The disk motor has an external rotor attached to
348-418: A bit cell comprising about 18 magnetic grains (11 by 1.6 grains). Since the mid-2000s, areal density progress has been challenged by a superparamagnetic trilemma involving grain size, grain magnetic strength and ability of the head to write. In order to maintain acceptable signal-to-noise, smaller grains are required; smaller grains may self-reverse ( electrothermal instability ) unless their magnetic strength
406-489: A breather port, unlike their air-filled counterparts. Other recording technologies are either under research or have been commercially implemented to increase areal density, including Seagate's heat-assisted magnetic recording (HAMR). HAMR requires a different architecture with redesigned media and read/write heads, new lasers, and new near-field optical transducers. HAMR is expected to ship commercially in late 2024, after technical issues delayed its introduction by more than
464-449: A component of the IBM 305 RAMAC system. It was approximately the size of two large refrigerators and stored five million six-bit characters (3.75 megabytes ) on a stack of 52 disks (100 surfaces used). The 350 had a single arm with two read/write heads, one facing up and the other down, that moved both horizontally between a pair of adjacent platters and vertically from one pair of platters to
522-1087: A decade, from earlier projections as early as 2009. HAMR's planned successor, bit-patterned recording (BPR), has been removed from the roadmaps of Western Digital and Seagate. Western Digital's microwave-assisted magnetic recording (MAMR), also referred to as energy-assisted magnetic recording (EAMR), was sampled in 2020, with the first EAMR drive, the Ultrastar HC550, shipping in late 2020. Two-dimensional magnetic recording (TDMR) and "current perpendicular to plane" giant magnetoresistance (CPP/GMR) heads have appeared in research papers. Some drives have adopted dual independent actuator arms to increase read/write speeds and compete with SSDs. A 3D-actuated vacuum drive (3DHD) concept and 3D magnetic recording have been proposed. Depending upon assumptions on feasibility and timing of these technologies, Seagate forecasts that areal density will grow 20% per year during 2020–2034. The highest-capacity HDDs shipping commercially in 2024 are 32 TB. The capacity of
580-411: A hard disk drive, as reported by an operating system to the end user, is smaller than the amount stated by the manufacturer for several reasons, e.g. the operating system using some space, use of some space for data redundancy, space use for file system structures. Confusion of decimal prefixes and binary prefixes can also lead to errors. Exabyte Too Many Requests If you report this error to
638-528: A price of US$ 3,499 . Later, a 10 MB model was offered, but required an upgraded PROM /interface card to recognize the additional 5 MB. Internally, the ProFile consisted of a bare Seagate ST-506 stepper motor drive and mechanism, without the usual Seagate electronics, a digital and an analog circuit board designed and manufactured by Apple, and a power supply. Later Lisa models could be configured with an internal 10 MB "Widget" voice-coil drive with
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#1732782813968696-681: A proprietary controller designed and built entirely by Apple, but the Widget was never offered as an external product for use with other Apple computers. Apple did not offer another hard drive until it released the Hard Disk 20 designed specifically for the Macintosh 512K in September 1985 which could not be used on the Apple II or III families, or Lisa series. The ProFile could not be used on
754-475: A removable disk module, which included both the disk pack and the head assembly, leaving the actuator motor in the drive upon removal. Later "Winchester" drives abandoned the removable media concept and returned to non-removable platters. In 1974, IBM introduced the swinging arm actuator, made feasible because the Winchester recording heads function well when skewed to the recorded tracks. The simple design of
812-538: A second set. Variants of the IBM 350 were the IBM 355 , IBM 7300 and IBM 1405 . In 1961, IBM announced, and in 1962 shipped, the IBM ;1301 disk storage unit, which superseded the IBM 350 and similar drives. The 1301 consisted of one (for Model 1) or two (for model 2) modules, each containing 25 platters, each platter about 1 ⁄ 8 -inch (3.2 mm) thick and 24 inches (610 mm) in diameter. While
870-616: A swing arm drive, the IBM 0680 (Piccolo), with eight inch platters, exploring the possibility that smaller platters might offer advantages. Other eight inch drives followed, then 5 + 1 ⁄ 4 in (130 mm) drives, sized to replace the contemporary floppy disk drives . The latter were primarily intended for the then fledgling personal computer (PC) market. Over time, as recording densities were greatly increased, further reductions in disk diameter to 3.5" and 2.5" were found to be optimum. Powerful rare earth magnet materials became affordable during this period, and were complementary to
928-423: A thin film of ferromagnetic material on both sides of a disk. Sequential changes in the direction of magnetization represent binary data bits . The data is read from the disk by detecting the transitions in magnetization. User data is encoded using an encoding scheme, such as run-length limited encoding, which determines how the data is represented by the magnetic transitions. A typical HDD design consists of
986-499: A tiny fraction of the detected errors end up as not correctable. Examples of specified uncorrected bit read error rates include: Within a given manufacturers model the uncorrected bit error rate is typically the same regardless of capacity of the drive. The worst type of errors are silent data corruptions which are errors undetected by the disk firmware or the host operating system; some of these errors may be caused by hard disk drive malfunctions while others originate elsewhere in
1044-730: A type of non-volatile storage , retaining stored data when powered off. Modern HDDs are typically in the form of a small rectangular box . Hard disk drives were introduced by IBM in 1956, and were the dominant secondary storage device for general-purpose computers beginning in the early 1960s. HDDs maintained this position into the modern era of servers and personal computers , though personal computing devices produced in large volume, like mobile phones and tablets , rely on flash memory storage devices. More than 224 companies have produced HDDs historically , though after extensive industry consolidation, most units are manufactured by Seagate , Toshiba , and Western Digital . HDDs dominate
1102-476: Is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnetic material. The platters are paired with magnetic heads , usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a random-access manner, meaning that individual blocks of data can be stored and retrieved in any order. HDDs are
1160-446: Is capable of scheduling reads and writes efficiently on the platter surfaces and remapping sectors of the media that have failed. Modern drives make extensive use of error correction codes (ECCs), particularly Reed–Solomon error correction . These techniques store extra bits, determined by mathematical formulas, for each block of data; the extra bits allow many errors to be corrected invisibly. The extra bits themselves take up space on
1218-590: Is commonly known as the " superparamagnetic limit ". To counter this, the platters are coated with two parallel magnetic layers, separated by a three-atom 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 (PMR), first shipped in 2005, and as of 2007 , used in certain HDDs. Perpendicular recording may be accompanied by changes in
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#17327828139681276-669: Is improving faster than HDDs. NAND has a higher price elasticity of demand than HDDs, and this drives market growth. During the late 2000s and 2010s, the product life cycle of HDDs entered a mature phase, and slowing sales may indicate the onset of the declining phase. The 2011 Thailand floods damaged the manufacturing plants and impacted hard disk drive cost adversely between 2011 and 2013. In 2019, Western Digital closed its last Malaysian HDD factory due to decreasing demand, to focus on SSD production. All three remaining HDD manufacturers have had decreasing demand for their HDDs since 2014. A modern HDD records data by magnetizing
1334-418: Is increased, but known write head materials are unable to generate a strong enough magnetic field sufficient to write the medium in the increasingly smaller space taken by grains. Magnetic storage technologies are being developed to address this trilemma, and compete with flash memory –based solid-state drives (SSDs). In 2013, Seagate introduced shingled magnetic recording (SMR), intended as something of
1392-460: Is shaped rather like an arrowhead and is made of doubly coated copper magnet wire . The inner layer is insulation, and the outer is thermoplastic, which bonds the coil together after it is wound on a form, making it self-supporting. The portions of the coil along the two sides of the arrowhead (which point to the center of the actuator bearing) then interact with the magnetic field of the fixed magnet. Current flowing radially outward along one side of
1450-588: Is specified in unit prefixes corresponding to powers of 1000: a 1- terabyte (TB) drive has a capacity of 1,000 gigabytes , where 1 gigabyte = 1 000 megabytes = 1 000 000 kilobytes (1 million) = 1 000 000 000 bytes (1 billion). Typically, some of an HDD's capacity is unavailable to the user because it is used by the file system and the computer operating system , and possibly inbuilt redundancy for error correction and recovery. There can be confusion regarding storage capacity, since capacities are stated in decimal gigabytes (powers of 1000) by HDD manufacturers, whereas
1508-589: The Apple Macintosh . Many Macintosh computers made between 1986 and 1998 featured a SCSI port on the back, making external expansion simple. Older compact Macintosh computers did not have user-accessible hard drive bays (indeed, the Macintosh 128K , Macintosh 512K , and Macintosh Plus did not feature a hard drive bay at all), so on those models, external SCSI disks were the only reasonable option for expanding upon any internal storage. HDD improvements have been driven by increasing areal density , listed in
1566-510: The Lisa computer, which was normally sold with a ProFile. The ProFile could be connected to the built-in parallel port of the Lisa, or to a port on an optional dual-port parallel interface card. Up to three such interface cards could be installed, so in principle up to seven ProFile drives could be used on a Lisa. The 5 MB ProFile was Apple's first hard drive, and was introduced in September 1981 at
1624-572: The Shannon limit and thus provide the highest storage density available. Typical hard disk drives attempt to "remap" the data in a physical sector that is failing to a spare physical sector provided by the drive's "spare sector pool" (also called "reserve pool"), while relying on the ECC to recover stored data while the number of errors in a bad sector is still low enough. The S.M.A.R.T ( Self-Monitoring, Analysis and Reporting Technology ) feature counts
1682-526: The HDD, but allow higher recording densities to be employed without causing uncorrectable errors, resulting in much larger storage capacity. For example, a typical 1 TB hard disk with 512-byte sectors provides additional capacity of about 93 GB for the ECC data. In the newest drives, as of 2009 , low-density parity-check codes (LDPC) were supplanting Reed–Solomon; LDPC codes enable performance close to
1740-481: The IBM GV (Gulliver) drive, invented at IBM's UK Hursley Labs, became IBM's most licensed electro-mechanical invention of all time, the actuator and filtration system being adopted in the 1980s eventually for all HDDs, and still universal nearly 40 years and 10 billion arms later. Like the first removable pack drive, the first "Winchester" drives used platters 14 inches (360 mm) in diameter. In 1978, IBM introduced
1798-652: The Macintosh or the Apple IIc (for which Apple never offered an external hard disk drive of any kind). By September 1986, the ProFile would be superseded by the introduction of the first cross-platform Hard Disk 20SC SCSI -based drive for the Macintosh and interface card for the Apple II family (excluding the IIc series, which had no SCSI interface of any kind) and Lisa/XL series. Hard disk drive A hard disk drive ( HDD ), hard disk , hard drive , or fixed disk
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1856-443: The arrowhead and radially inward on the other produces the tangential force . 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 north pole and half south 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
1914-450: The case of embedded servo, otherwise known as sector servo technology). The servo feedback optimizes the signal-to-noise ratio of the GMR sensors by adjusting the voice coil motor to rotate the arm. A more modern servo system also employs milli and/or micro actuators to more accurately position the read/write heads. The spinning of the disks uses fluid-bearing spindle motors. Modern disk firmware
1972-441: The connection between the drive and the host. The rate of areal density advancement was similar to Moore's law (doubling every two years) through 2010: 60% per year during 1988–1996, 100% during 1996–2003 and 30% during 2003–2010. Speaking in 1997, Gordon Moore called the increase "flabbergasting", while observing later that growth cannot continue forever. Price improvement decelerated to −12% per year during 2010–2017, as
2030-449: The disks; the stator windings are fixed in place. Opposite the actuator at the end of the head support arm is the read-write head; thin printed-circuit cables connect the read-write heads to amplifier electronics mounted at the pivot of the actuator. The head support arm is very light, but also stiff; in modern drives, acceleration at the head reaches 550 g . The actuator is a permanent magnet and moving coil motor that swings
2088-467: The earlier IBM disk drives used only two read/write heads per arm, the 1301 used an array of 48 heads (comb), each array moving horizontally as a single unit, one head per surface used. Cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches (about 6 μm) above the platter surface. Motion of the head array depended upon a binary adder system of hydraulic actuators which assured repeatable positioning. The 1301 cabinet
2146-443: The growth of areal density slowed. The rate of advancement for areal density slowed to 10% per year during 2010–2016, and there was difficulty in migrating from perpendicular recording to newer technologies. As bit cell size decreases, more data can be put onto a single drive platter. In 2013, a production desktop 3 TB HDD (with four platters) would have had an areal density of about 500 Gbit/in which would have amounted to
2204-416: The heads to the desired position. A metal plate supports a squat 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 have only one magnet). The voice coil itself
2262-427: The largest hard drive had a capacity of 15 TB, while the largest capacity SSD had a capacity of 100 TB. As of 2018 , HDDs were forecast to reach 100 TB capacities around 2025, but as of 2019 , the expected pace of improvement was pared back to 50 TB by 2026. Smaller form factors, 1.8-inches and below, were discontinued around 2010. The cost of solid-state storage (NAND), represented by Moore's law ,
2320-444: The magnetization of the material passing immediately under it. In modern drives, 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,
2378-422: The manufacturing of the read/write heads to increase the strength of the magnetic field created by the heads. In 2004, a higher-density recording media was introduced, consisting of coupled soft and hard magnetic layers. So-called exchange spring media magnetic storage technology, also known as exchange coupled composite media , allows good writability due to the write-assist nature of the soft layer. However,
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2436-420: The most commonly used operating systems report capacities in powers of 1024, which results in a smaller number than advertised. Performance is specified as the time required to move the heads to a track or cylinder (average access time), the time it takes for the desired sector to move under the head (average latency , which is a function of the physical rotational speed in revolutions per minute ), and finally,
2494-559: The norm in most computer installations and reached capacities of 300 megabytes by the early 1980s. Non-removable HDDs were called "fixed disk" drives. In 1963, IBM introduced the 1302, with twice the track capacity and twice as many tracks per cylinder as the 1301. The 1302 had one (for Model 1) or two (for Model 2) modules, each containing a separate comb for the first 250 tracks and the last 250 tracks. Some high-performance HDDs were manufactured with one head per track, e.g. , Burroughs B-475 in 1964, IBM 2305 in 1970, so that no time
2552-534: The platters, increasing areal density. Normally hard drive recording heads have a pole called a main pole that is used for writing to the platters, and adjacent to this pole is an air gap and a shield. The write coil of the head surrounds the pole. The STO device is placed in the air gap between the pole and the shield to increase the strength of the magnetic field created by the pole; FC-MAMR technically doesn't use microwaves, but uses technology employed in MAMR. The STO has
2610-416: The revenue of hard disk drives as of 2017 . Though SSDs have four to nine times higher cost per bit, they are replacing HDDs in applications where speed, power consumption, small size, high capacity and durability are important. As of 2019 , the cost per bit of SSDs is falling, and the price premium over HDDs has narrowed. The primary characteristics of an HDD are its capacity and performance . Capacity
2668-427: The speed at which the data is transmitted (data rate). The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as SATA (Serial ATA), USB , SAS ( Serial Attached SCSI ), or PATA (Parallel ATA) cables. The first production IBM hard disk drive, the 350 disk storage , shipped in 1957 as
2726-438: The stack of disk platters when the drive was powered down. Instead, the heads were allowed to "land" on a special area of the disk surface upon spin-down, "taking off" again when the disk was later powered on. This greatly reduced the cost of the head actuator mechanism, but precluded removing just the disks from the drive as was done with the disk packs of the day. Instead, the first models of "Winchester technology" drives featured
2784-450: The swing arm actuator design to make possible the compact form factors of modern HDDs. As the 1980s began, HDDs were a rare and very expensive additional feature in PCs, but by the late 1980s, their cost had been reduced to the point where they were standard on all but the cheapest computers. Most HDDs in the early 1980s were sold to PC end users as an external, add-on subsystem. The subsystem
2842-439: The table above. Applications expanded through the 2000s, from the mainframe computers of the late 1950s to most mass storage applications including computers and consumer applications such as storage of entertainment content. In the 2000s and 2010s, NAND began supplanting HDDs in applications requiring portability or high performance. NAND performance is improving faster than HDDs, and applications for HDDs are eroding. In 2018,
2900-400: The thermal stability is determined only by the hardest layer and not influenced by the soft layer. Flux control MAMR (FC-MAMR) allows a hard drive to have increased recording capacity without the need for new hard disk drive platter materials. MAMR hard drives have a microwave generating spin torque generator (STO) on the read/write heads which allows physically smaller bits to be recorded to
2958-475: The top and bottom of the coil produce radial forces that do not rotate the head. The HDD's electronics controls the movement of the actuator and the rotation of the disk and transfers data to/from a 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
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#17327828139683016-491: The total number of errors in the entire HDD fixed by ECC (although not on all hard drives as the related S.M.A.R.T attributes "Hardware ECC Recovered" and "Soft ECC Correction" are not consistently supported), and the total number of performed sector remappings, as the occurrence of many such errors may predict an HDD failure . The "No-ID Format", developed by IBM in the mid-1990s, contains information about which sectors are bad and where remapped sectors have been located. Only
3074-433: The usual filtered air. Since turbulence and friction are reduced, higher areal densities can be achieved due to using a smaller track width, and the energy dissipated due to friction is lower as well, resulting in a lower power draw. Furthermore, more platters can be fit into the same enclosure space, although helium gas is notoriously difficult to prevent escaping. Thus, helium drives are completely sealed and do not have
3132-499: The volume of storage produced ( exabytes per year) for servers. Though production is growing slowly (by exabytes shipped ), sales revenues and unit shipments are declining, because solid-state drives (SSDs) have higher data-transfer rates, higher areal storage density, somewhat better reliability, and much lower latency and access times. The revenues for SSDs, most of which use NAND flash memory , slightly exceeded those for HDDs in 2018. Flash storage products had more than twice
3190-520: Was about the size of three large refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes per module. Access time was about a quarter of a second. Also in 1962, IBM introduced the model 1311 disk drive, which was about the size of a washing machine and stored two million characters on a removable disk pack . Users could buy additional packs and interchange them as needed, much like reels of magnetic tape . Later models of removable pack drives, from IBM and others, became
3248-427: Was lost physically moving the heads to a track and the only latency was the time for the desired block of data to rotate into position under the head. Known as fixed-head or head-per-track disk drives, they were very expensive and are no longer in production. In 1973, IBM introduced a new type of HDD code-named " Winchester ". Its primary distinguishing feature was that the disk heads were not withdrawn completely from
3306-513: Was not sold under the drive manufacturer's name but under the subsystem manufacturer's name such as Corvus Systems and Tallgrass Technologies , or under the PC system manufacturer's name such as the Apple ProFile . The IBM PC/XT in 1983 included an internal 10 MB HDD, and soon thereafter, internal HDDs proliferated on personal computers. External HDDs remained popular for much longer on
3364-408: Was the norm. As of November 2019 , the platters in most consumer-grade HDDs spin at 5,400 or 7,200 rpm. Information is written to and read from a platter as it rotates past devices called read-and-write heads that are positioned to operate very close to the magnetic surface, with their flying height often in the range of tens of nanometers. The read-and-write head is used to detect and modify
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