Optical media offer the following advantages for storing data over conventional magnetic disks:
Because optical media are usually written to and read with a laser, a bit of data is written to a much smaller area on the optical platter (disc) than the area that is required to record a bit on a conventional magnetic disk. Optical platters offer a high degree of stability because they are far less susceptible than magnetic disks to corruption by environmental influences such as electromagnetic fields. Furthermore, the possibility of a read/write head crash is extremely remote because the optical disc read/write head does not come as close to the platter as the magnetic disk read/write head.
The Optical Subsystem supports only the write-once-read-many (WORM) type of optical media. When data is written to WORM optical media, a permanent, virtually incorruptible mark is made on the platter. Thereafter, you can read the data an unlimited number of times. When you update the data to a WORM optical platter, it is written to a new location on the platter; the optical-storage subsystem cannot reuse the original location.
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