In information technology, backup refers to making copies of data so that these additional copies may be used to restore the original after a data loss event.
These additional copies are typically called "backups." Backups are useful primarily for two purposes.
The first is to restore a state following a disaster (called disaster recovery). The second is to restore small numbers of files after they have been accidentally deleted or corrupted.
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.
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