What is a differential backup?A differential backup is a backup of every file on a filesystem which has been modified since the last full backup. The alternatives to a differential backup are incremental backup and full backup. A differential backup can provide an optimal middle-ground between an incremental backup and a full-backup. A differential backup is faster than a full backup, but not as fast as an incremental backup. A differential backup requires less storage space than a full backup, but more storage space than an incremental backup. A differential backup requires less time to restore than an incremental backup, but more time to restore than a full backup. If you perform a full backup on Saturday and a differential every night, and the system crashes on Wednesday, you will only need to restore the full backup from Saturday and the differential backup from Tuesday. In contrast, if you perform a full backup on Saturday and incremental backups every night, when the system crashes on Wednesday, you will need to restore the full backup from Saturday along with the incremental backups from Sunday, Monday, and Tuesday. A differential backup should be performed daily on production systems.
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