In IT, a backup, or data backup is a copy/snapshot of computer data taken and stored so that it may be used to restore the original after a data loss event.Backups can be used to recover data after its loss from data deletion or corruption, or to recover data from an earlier time. 

Backups provide a simple form of disaster recovery; however not all backup systems are able to reconstitute a computer system or other complex configuration such as a computer cluster, active directory server, or database server