backup:    1. n. A collection of data stored on (usually removable) non-volatile storage media for purposed of recovery in case the original copy of the data is lost or becomes inaccessible. Also called a backup copy. To be useful for recovery, a backup must be made by copying the source data image when it is in a consistent state. 2. n. A process that creates a backup (definition 1). 3. v. The act of creating a backup. cf. archive.

See also: backup strategies, cumulative incremental backup, differential incremental backup, full backup, incremental backup, [ITIL] Backup

Concepts

Backup is the process of copying a collection of data, the object, from “primary” to “secondary” storage for the purpose of recovery in the event of failure. Its complement is Recovery, the process invoked on failure or other requirement to return the contents of the collection to primary storage. To be useful for recovery, the source data image needs to be in a consistent state during the backup. The copy should provide a non-volatile point of retrieval. In addition, a data object may have multiple copies or recovery points. Failure causes may be logical, physical, accidental or intentional resulting in loss or inaccessibility of the original data. The primary storage is typically disk. The secondary storage is typically magnetic tape, often called removable media because it is easy to transport to an alternate location. Today, disk/tape combinations and remote disks may serve as secondary storage in addition to other media forms. An alternate location or site is required in the event of primary site destruction or that the site becomes unavailable. In most cases, the legal or insurance test of backup "validity" requires a combination of the ability to recover from the media and physical storage of the media at a specified minimum distance form the primary site.

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