Disk storage
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Disk storage is a category of data storage mechanisms for computers; data is recorded on planar surfaces or 'disks' for temporary or permanent storage. A disk drive is a peripheral device used to read from and write to a disk.
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 The drum was superseded by disks, as the lower mass and inertia allowed smaller and lighter devices. Reynold Johnson an inventor who worked for IBM for many years is said to be the "father" of the disk drive.
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.
In disk storage, there are the two primary access methods. Block storage means that the disk is divided into normally equal-sized blocks which are accessed at random by the operating system. File storage contains an abstraction of files and directories which can be used to refer to storage content. Another access method, content-addressable storage (CAS) uses a hashing algorithm to refer to pieces of data.
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[edit] External links
- More Bits in Pits - article by JR Minkel
