disk pack

views updated

disk pack One form of exchangeable disk store, now obsolete, that consisted of an assembly of identical 14 diameter rigid magnetic disks mounted coaxially and equally spaced. A similar nonrecording protective disk was fitted above the top recording disk with another one below the bottom recording disk. The whole assembly was rigidly clamped together, and was designed for dynamic stability at high rotation on a disk drive. The whole pack, when not mounted on the drive, was contained within sealed plastic covers, in two parts, which helped to ensure that the pack was protected from damage, dust, and contamination. The bottom cover was removed before mounting the pack on the drive; the top cover could only be removed when the pack had been mounted.

Storage capacities ranged from 30 to 300 megabytes, over the range of track densities up to 400 tracks per inch, recording densities up to 6000 bits per inch, and pack sizes of 5 to 12 disks. Disk packs were introduced by IBM in 1963, and most types are subjects of international standards.