Hard disk drive

A hard disk drive (HDD), hard disk, hard drive, or fixed disk, is an electromechanical data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material.

A hard disk drive platter (or disk) is the circular disk on which magnetic data is stored in a hard disk drive.

A hard disk drive (HDD), hard disk, hard drive, or fixed disk, is an electromechanical data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material.

, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals.

Introduced by IBM in 1956, HDDs became the dominant secondary storage device for general-purpose computers by the early 1960s.

Inventions by IBM include the automated teller machine (ATM), the floppy disk, the hard disk drive, the magnetic stripe card, the relational database, the SQL programming language, the UPC barcode, and dynamic random-access memory (DRAM).

More than 200 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital.

Western Digital Corporation (abbreviated WDC, commonly known as Western Digital and abbreviated WD) is an American computer hard disk drive manufacturer and data storage company.

Introduced by IBM in 1956, HDDs became the dominant secondary storage device for general-purpose computers by the early 1960s.

Hard disks were also starting to grow popular.

More than 200 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital.

Seagate developed the first 5.25-inch hard disk drive (HDD), the 5-megabyte ST-506, in 1980.

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.

As of 2019 hard disk drives have been key storage devices and are projected to remain so for the foreseeable future.

Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially.

In computer science, sequential access means that a group of elements (such as data in a memory array or a disk file or on magnetic tape data storage) is accessed in a predetermined, ordered sequence.

HDDs are a type of non-volatile storage, retaining stored data even when powered off.

Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer storage devices (e.g. hard disk drives, solid state drives, floppy disks, and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards.

HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB or SAS (Serial Attached SCSI) cables.

In computing, Serial Attached SCSI (SAS) is a point-to-point serial protocol that moves data to and from computer-storage devices such as hard drives and tape drives.

The subsystem 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.

Tallgrass Technologies Corporation was the first manufacturer to offer a hard disk drive product for the IBM PC. Tallgrass was a Kansas City based microcomputer hardware and software company founded in December 1980 by David M. Allen.

The subsystem 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.

Corvus was a pioneer of the early days of personal computers, producing the first hard disk drives, data backup, and networking devices, commonly for the Apple II series.

The subsystem 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 ProFile was the first hard disk drive produced by Apple Computer, initially for use with the Apple III personal computer.

Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially.

Blocking is almost universally employed when storing data to 9-track magnetic tape, NAND flash memory, and rotating media such as floppy disks, hard disks, and optical discs.

The IBM PC/XT in 1983 included an internal 10 MB HDD, and soon thereafter internal HDDs proliferated on personal computers.

The IBM Personal Computer XT, often shortened to the IBM XT, PC XT, or simply XT, is a version of the IBM PC with a built-in hard drive.

Capacity is specified in unit prefixes corresponding to powers of : a 1-terabyte (TB) drive has a capacity of gigabytes (GB; where 1 gigabyte = bytes).

Hard disk drives: 2007 (decimal usage)

Capacity is specified in unit prefixes corresponding to powers of : a 1-terabyte (TB) drive has a capacity of gigabytes (GB; where 1 gigabyte = bytes).

This definition is used in networking contexts and most storage media, particularly hard drives, flash-based storage, and DVDs, and is also consistent with the other uses of the SI prefix in computing, such as CPU clock speeds or measures of performance.

Market 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.

Devices and/or systems that have been described as mass storage include tape libraries, RAID systems, and a variety of computer drives such as hard disk drives, magnetic tape drives, magneto-optical disc drives, optical disc drives, memory cards, and solid-state drives.

Continuously improved, HDDs have maintained this position into the modern era of servers and personal computers.

A typical desktop computer consists of a computer case (or "tower"), a metal chassis that holds the power supply, motherboard, hard disk drive, and often an optical disc drive.

Another technology used to overcome thermal effects to allow greater recording densities is perpendicular recording, first shipped in 2005, and as of 2007 the technology was used in many HDDs.

Perpendicular recording (or perpendicular magnetic recording, PMR) is a technology for data recording on magnetic media, particularly hard disks.

More than 200 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital.

In January 2009, Toshiba acquired the HDD business of Fujitsu.

A modern HDD records data by magnetizing a thin film of ferromagnetic material on a disk.

Ferromagnetism is very important in industry and modern technology, and is the basis for many electrical and electromechanical devices such as electromagnets, electric motors, generators, transformers, and magnetic storage such as tape recorders, and hard disks, and nondestructive testing of ferrous materials.

Capacity is specified in unit prefixes corresponding to powers of : a 1-terabyte (TB) drive has a capacity of gigabytes (GB; where 1 gigabyte = bytes).

In the specifications of hard disk drive capacities and network transmission bit rates, on the other hand, decimal prefixes, consistent with the metric system, are used.

The arm is moved using a voice coil actuator or in some older designs a stepper motor.

The term is also used for voice coil linear motors, such as those used to move the heads inside hard disk drives, which produce a larger force and move a longer distance but work on the same principle.

A metal plate supports a squat neodymium-iron-boron (NIB) high-flux magnet.

They have replaced other types of magnets in many applications in modern products that require strong permanent magnets, such as motors in cordless tools, hard disk drives and magnetic fasteners.