Backup

Backup is a process used essentially universally throughout computing: it involves making a copy (usually also called a 'backup') of newly-created data, so that should a hardware failure occur in the device holding the data, it is not lost.

The backup may simply be a copy made on identical media to that holding the original (e.g. a disk pack), or it may be on another medium: for a long time, magnetic tape was used, since it had high capacity, but was fairly inexpensive.