disk drive

(redirected from Disk drives)
Also found in: Dictionary, Thesaurus, Medical, Financial.

disk drive

Computing the controller and mechanism for reading and writing data on computer disks

disk drive

[′disk ‚drīv]
(computer science)
The physical unit that holds, spins, reads, and writes the magnetic disks. Also known as disk unit.

disk drive

(hardware, storage)
(Or "hard disk drive", "hard drive", "floppy disk drive", "floppy drive") A peripheral device that reads and writes hard disks or floppy disks. The drive contains a motor to rotate the disk at a constant rate and one or more read/write heads which are positioned over the desired track by a servo mechanism. It also contains the electronics to amplify the signals from the heads to normal digital logic levels and vice versa.

In order for a disk drive to start to read or write a given location a read/write head must be positioned radially over the right track and rotationally over the start of the right sector.

Radial motion is known as "seeking" and it is this which causes most of the intermittent noise heard during disk activity. There is usually one head for each disk surface and all heads move together. The set of locations which are accessible with the heads in a given radial position are known as a "cylinder". The "seek time" is the time taken to seek to a different cylinder.

The disk is constantly rotating (except for some floppy disk drives where the motor is switched off between accesses to reduce wear and power consumption) so positioning the heads over the right sector is simply a matter of waiting until it arrives under the head. With a single set of heads this "rotational latency" will be on average half a revolution but some big drives have multiple sets of heads spaced at equal angles around the disk.

If seeking and rotation are independent, access time is seek time + rotational latency. When accessing multiple tracks sequentially, data is sometimes arranged so that by the time the seek from one track to the next has finished, the disk has rotated just enough to begin accessing the next track.

See also sector interleave.

The disks may be removable disks; floppy disks always are, removable hard disks were common on mainframes and minicomputers but less so on microcomputers until the mid 1990s(?) with products like the Zip Drive.

A CD-ROM drive is not usually referred to as a disk drive.

Two common interfaces for disk drives (and other devices) are SCSI and IDE. ST-506 used to be common in microcomputers (in the 1980s?).

disk drive

A storage device that holds, spins, reads and writes magnetic disks or optical discs (CD, DVD, MO, UDO). In this encyclopedia, disk ("k") refers to a magnetic disk drive, and disc ("c") means an optical drive. Magnetic disk drives contain non-removable platters; however, optical drives are receptacles for removable discs or cartridges. See magnetic disk, CD, DVD, magneto-optic disk and UDO.

The Early 1990s
This RAID II prototype in 1992, which embodied the principles of high performance and fault tolerance, was built by University of Berkeley graduate students. Housing 36 320MB disk drives, its total storage was less than the single drive in the cheapest PC only six years later. (Image courtesy of The Computer History Museum, www.computerhistory.org) See RAID.
References in periodicals archive ?
Hitachi is committed to being the preeminent supplier of disk drives to the consumer electronics marketplace.
Today, disk drive technology covers a wide range of users and systems from notebook computers to hand held consumer devices," said Dr.
Storage administrators have become increasingly cautious about allocating too many applications or over-allocating storage on a disk drive in order to maintain acceptable levels of response time and device performance.
5" external hard disk drive line from our competition.
Since more disk drives are required, RAID 5+1 is even more expensive than RAID 1+0.
As the price per megabyte for high-end disk drives decreases rapidly, there is a major impact on sales revenues for mainframe computer disk drive arrays, which tend to use a large number of drives.
SAS disk drives are designed to withstand the demands of high-duty cycle enterprise storage applications.
CleanFlex utilizes Carbon Dioxide snow to remove particulates and organic contamination from reworked and new drives leaving the disk drives pristine.
This backend consists of both the disk drives and the management applications.
With its ample amounts of SDRAM, streams can be interleaved to deep memory buffers to ensure sensor data isn't lost to irregular transfer rates inherent to secondary storage media based on hard disk drives," said Mike Jadon, Director of Product Marketing for Micro Memory.