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Write Once, Read Many (WORM) |
WORM (for write once, read many) is a data storage technology
that allows information to be written to a disk a single time and prevents
the drive from erasing the data. The disks are intentionally not rewritable,
because they are especially intended to store data that the user does not
want to erase accidentally. Because of this feature, WORM devices have long
been used for the archival purposes of organizations such as government
agencies or large enterprises. A type of optical media, WORM devices were
developed in the late 1970s and have been adapted to a number of different
media. The disks have varied in size from 5.25 to 14 inches wide, in varying
formats ranging from 140MB to more than 3 GB per side of the (usually) double-sided
medium. Data is written to a WORM disk with a low-powered laser that makes
permanent marks on the surface.
Because of a lack of standardization, WORM disks have typically been only
readable by the drive on which they were written, and hardware and software
incompatibility has hampered their marketplace acceptance. Other optical
media, such as CDs and DVDs that can be recorded once and read an unlimited
number of times are sometimes considered WORM devices, although there is
some argument over whether formats that can be written in more than one
session (such as the multisession CD) qualify as such. CD-R has gradually
been replacing traditional WORM devices, and it is expected that some newer
technology, such as DVD-R or HD-ROM will eventually replace both WORM and
CD-R devices.
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