Differential Backup

Definition - What does Differential Backup mean?

Differential backup is a data backup procedure that records data changes that have occurred since the most recent full backup. Differential backup only saves the new data or data that has changed since the last full backup; it does not make a backup of all the data every single time. The benefit of using differential backup, versus a full or incremental backup, is that it takes a relatively shorter amount of time to restore the data. However, if done several times without occasionally performing a full backup, the size of the differential backup can grow larger than the baseline full backup.

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Techopedia explains Differential Backup

The definitions of differential and incremental backup can be quite confusing and are often interchanged by users. Incremental backup also copies files that were added and considered as changes, but the main difference between the two is that incremental backup copies the data until the last backup only, whatever type of backup that might be, while differential backup copies until the last full backup.

To better understand the difference, consider the scenario of a student that performed a full backup of his files on Wednesday. On Thursday, he performed a differential backup, which saved the changes made since Wednesday. On Saturday, the student performed a differential backup again, which saved all changes that were made since his full backup on Wednesday. On the other hand, if he used incremental backup throughout, the backup made on Saturday would only reflect as far back as Thursday.

The advantages of differential backup include:

It involves less storage drive space than incremental backups.
The amount of time for backup is much quicker than full or incremental backups.

The disadvantages include:

Restoring files may take longer since it may have to be done from both the full and differential backup.
Restoring individual files might take a while since it has to be searched from either the full or differential backup.