Incremental backup

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An incremental backup is a backup method where multiple backups are kept (not just the last one). These backups will be incremental if each original piece of backed up information is stored only once, and then successive backups only contain the information that changed since the previous one.

As a backup method, it is highly efficient, since it allows for the storage of N copies of size S information chunks, with a total storage requirement much lower than NxS. If the original information that is backed up does not change between backups, the total size will approach just S. If it changes almost completely, the NxS limit will be approached.

1 Variants
2 See also

[edit] Variants

[edit] Differential backup

A cumulative backup of all changes made after the last full backup. The advantage to this is the quicker recovery time, requiring only a full backup and the latest differential backup to restore the system. The disadvantage is that for each day elapsed since the last full backup, more data needs to be backed up, especially if a majority of the data has been changed.

[edit] Multilevel incremental

A more sophisticated incremental backup scheme involves multiple numbered backup levels. A full backup is level 0. A level n backup will backup everything since the most recent level n-1 backup. Assume a level 0 backup was taken on a Sunday. A level 1 backup taken on Monday would only include changes made since Sunday. A level 2 backup taken on Tuesday would only include changes made since Monday. A level 3 backup taken on Wednesday would only include changes made since Tuesday. If a level 2 backup was taken on Thursday, it would include all changes made since Monday because Monday was the most recent level n-1 backup.

[edit] Reverse incremental

An incremental backup of the changes made between two instances of a mirror is called a reverse incremental. By applying a reverse incremental to a mirror, the result will be a previous version of the mirror.