What's the difference between a differential and an incremental backup? How does the backup type impact recovery?

SUMMARY

This article explains the differences between the differential and incremental backup types as well as the restore effects

ISSUE

Both differential and incremental backups are partial backups, meaning they don't capture all data present on a file system. They only capture data that has changed since a previous backup. Differential backups include all data that has changed since the last master. Incremental backups include all data that has changed since the last backup of any type. This means that if you are running a master on Sunday, a differential on Monday will back up all the changes since Sunday, and a differential on Friday will also back up all the changes since Sunday. Likewise, if you're running a master on Sunday, an incremental on Monday will back up the changes since Sunday, an incremental on Tuesday will back up the changes since Monday, and so on. For graphical representations of differential and incremental backups, see the following sections in the Recovery-Series and UEB Administrator's Guide: Incremental backup and Differential backup.

Each backup creates a recovery point of the entire asset. It contains the data captured during the backup job, plus all dependent data in the backup group. You can recover entire backups or pick a subset of files. Recovering an entire backup recovers all dependent data in the group. For example, recovering an incremental also recovers its parent full and any other dependent incrementals in the chain. 

It is faster to restore data from a differential backup than an incremental. An incremental backup takes less time to run.

Please also note that due to the Incremental Forever autosynth process, in which the Unitrends system rolls up your incremental backups into masters and differentials, running all incremental backups does NOT save space on your Unitrends system. See Synthetic backups and the Backups Overview in the Recovery-Series and UEB Administrator's Guide for details.

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