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Unix Backup and Recovery by W. Curtis Preston

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Optical Drives

Optical drives of various types are finally beginning to gain acceptance. They have always been popular with a small crowd because of their very short time-to-data values. Once mounted, some of them are as fast as disk when randomly accessing files. This is not something you can say for tapes. There are two reasons that optical drives are now gaining more acceptance. Their cost is dropping relative to tape technology, and their capacities and transfer speeds have dramatically increased in the last few years.

This section is divided into four main subsections: optical recording methods, CD recording formats, DVD recording formats, and magneto-optical recording Formats. Throughout, a recording method refers to how the data is physically represented on disk, and a recording format refers to what type of drive may use these recording formats. For example, the most common recording method is the phase change method. There are several formats that use this, such as CD-RW, DVD-RW, DVD-RAM, and DVD+RW.

Optical Recording Methods

Optical recording methods can be divided into two categories, recordable and rewritable. Recordable technologies produce read-only disks, while rewritable technologies allow a disk to be overwritten many times. Within each of these categories, there are several different competing recording methods.

Most people understand that traditional disk drives record digital (binary) data by polarizing sections of the disk. With most optical recording methods, ...

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