In the field of information technology, backup refers to the copying of data so that these additional copies may be restored after a data loss event. Backups are useful primarily for two purposes: to restore a computer to an operational state following a disaster (called disaster recovery) and to restore small numbers of files after they have been accidentally deleted or corrupted. Backups differ from archives in the sense that archives are the primary copy of data and backups are a secondary copy of data. Backup systems differ from fault-tolerant systems in the sense that backup systems assume that a fault will cause a data loss event and fault-tolerant systems assume a fault will not. Backups are typically that last line of defense against data loss, and consequently the least granular and the least convenient to use.

Since a backup system contains at least one copy of all data worth saving, the data storage requirements are considerable. Organizing this storage space and managing the backup process is a complicated undertaking.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Metasyntactic variable".

Source from:http://en.wikipedia.org

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