Disk storage

Disk storage is a group of data storage mechanisms for computers; data is transferred to planar surfaces or disks for temporary or permanent storage. In the early 1960s single data bits were stored as magnetic charges in magnetic core memory. The scientists at IBM in San Jose, California successfully created a rotating drum that was coated in a magnetically polarizable film that could be used to store data by changing and sensing magnetic polarization. The drum was superseded by disks, as the lower mass and inertia allowed smaller and lighter devices.

In musical and audio data storage, the first devices were also drum shaped, called phonograph cylinders, which were popularized by Thomas Edison. In the 1910s these were replaced as the dominant medium of sound recording by analogue disc records, commonly called gramophone records (in British English) or phonograph records (in American English). From the 1950s through the 1980s, audio recordings were also done on magnetic tape media of several types, although the vinyl record remained the most popular medium for home use. These were mostly replaced by compact disc technology, where the data is recorded in a digital format as optical information. This compact disc technology has been widely accepted, and data storage, using writable compact disks or CD-R devices is very common.

The random-access, low-density storage of disks has historically been complemented by the sequential-access high density storage provided by magnetic tape. Vigorous innovation in disk storage technology, coupled with less vigorous innovation in tape storage, has reduced the density and cost per bit gap between disk and tape, reducing the importance of tape as a complement to disk.

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Appropriate for this page would be things common to all disk based storage devices, that is a discussion of rotation (CLV, CAV). Low level formatting tracks, sectors, cylinders, platters, heads. rotational delay, seek time.