Tertiary Storage

Tertiary Storage

The biggest databases today need more than disks. Several kinds of tertiary storage devices have been developed. Tertiary devices, perhaps storing a terabyte each, need much more time to access a given item than does a disk. While typical disks can access any item in 10-20 milliseconds, a tertiary device may take several seconds. Tertiary storage devices involve transporting an object, upon which the desired data item is stored, to a reading device. This movement is carried out by a robotic conveyance of some kind.

For example, compact disks (CD's) or digital versatile disks (DVD's) may be the storage medium in a tertiary device. An arm mounted on a track goes to a particular disk, picks it up, carries it to a reader, and loads the disk into the reader.

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