Term:differential backup

A differential backup includes all files changed since the first full backup of a series. The term derives from the word “difference,” in that only the difference of the entire collection of files will be included.

Differential backups are used in conjunction with full backups as space-saving alternatives to backing up everything every time.

A differential backup is used when backups are taken periodically. The first is a full backup of everything. Each subsequent differential backup in the series, backing up all files modified since the first backup. This is in contrast to an “incremental” backup, which includes only those files changed since the immediately preceding backup.

While differential backups save space, they have a built-in dependency: to recover an entire collection of files to its most recent state, the initial full backup must also be available.

A differential backup is a type of data backup that preserves data, saving only the difference in the data since the last full backup. The rationale in this is that, since changes to data are generally few compared to the entire amount of data in the data repository, the amount of time required to complete the backup will be smaller than if a full backup was performed every time that the organization or data owner wishes to back up changes since the last full backup. Another advantage, at least as compared to the incremental backup method of data backup, is that at data restoration time, at most two backup media are ever needed to restore all the data. This simplifies data restores as well as increases the likelihood of shortening data restoration time.

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