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Definition: 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.