Backups have two distinct purposes
The primary purpose is to recover data after its loss, be it by data deletion or corruption. Data loss can be a common experience of computer users; a recent survey found that 66% of respondents had lost files on their PC. The secondary purpose of backups is to recover data from an earlier time, according to a user-defined data retention policy, typically configured within a backup application for how long copies of data are required. Though backups represent a simple form of disaster recovery and should be part of any disaster recovery plan, backups by themselves should not be considered a complete disaster recovery plan. One reason for this is that 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 by simply restoring data from a backup.
