Differential Backup

A differential backup is a backup of every file on a file system which has changed since the last full backup.

The alternatives to a differential backup are incremental backup and full backup.

A differential backup can be an optimal middle-ground between a full backup and an incremental backup.

A differential backup is not as fast as an incremental backup, but it is faster than a full backup. A differential backup requires more storage space than an incremental backup, but less than a full backup.

A differential backup requires more time to restore than a full backup, but not as much time to restore as an incremental backup.

If you perform a full backup on Sunday and a differential every night, and the system crashes on Thursday, you will only need to restore the full backup from Sunday and the differential backup from Wednesday.

In contrast, if you perform a full backup on Sunday and incremental backups every night, when the system crashes on Thursday, you will need to restore the full backup from Sunday along with the incremental backups from Monday, Tuesday, and Wednesday.

A differential backup should be performed daily on production systems.