This Week, Industry Snapshot Looks at
Storage Technology

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Quantum Corporation

Read-Rite Corporation

Seagate Technology, Inc.

Storage Technology Corporation

Western Digital Corporation

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This Week's Industry Snapshot

Disk drives are often referred to as hard drives, magnetic drives, Winchester drives, or occasionally they are just mentioned in tandem with a torrent of expletives as they crash. All these terms refer to memory devices that store information on rigid, continuously spinning, magnetically coated disks. Disk drives are distinguishable from other memory devices that also use disks to store data. Floppy drives, as the name implies, refers to removable, flexible disks that have capacities that are considerably less than hard drives. Laser or "optical" drives record information using light. Some of these optical drives have significantly greater capacity than their less sophisticated cousins, but are hampered by a much slower recording speed.

The rise to prominence of disk drives can be attributed to a basic performance and value proposition that made them the superior vehicle for data storage. Indeed, disk drives are the principal storage devices for data in almost all computers. In theory, all memory requirements could be handled by semiconductor devices, but due to their higher cost they are only employed when information must be available to the computer very quickly.

Spinning the Platters

Disk drives store data on perpetually spinning disks usually made of aluminum or glass and coated on both sides with a thin film of magnetic material. Magnetic heads, or "sliders," write and retrieve data on both sides of the disk by changing the magnetic state of very small areas on the disk surface. The same heads also perform a "reading" function by detecting the magnetized areas as the disk passes under the head, thus magnetized heads are sometimes referred to according to their "read/write" function. Data is arranged on the disks in concentric circles that are very closely spaced. A positioning device called an actuator moves the heads rapidly from track to track as determined by the controller in the disk drive. Disk drive heads are not in actual contact with the disk at any time; instead, the rapidly spinning disk entrains air and forces it under the head causing it to "fly" just above the surface. The closer the head flies to the disk the smaller the magnetic spot it can write and read, hence increasing the amount of data that can be stored. Clearances of 1 to 2 microinches are now common, which is an incredible feat when one considers that a strand of human hair is 3,000 microinches thick.

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