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FAQ: What are Incremental and Differential Backups?


What are incremental and differential backups?

This article applies to:

Carbonite Plans Products Platforms
Power and Ultimate (Not sure?) Carbonite Safe Server Backup (Not sure?) Windows


Incremental and Differential backups are the primary means by which Carbonite Safe Server Backup (CSSB) reduces the size of backup runs after the Full Backup. Incremental and Differential backups are very similar, but have several key differences in how they function.

There are also some requirements that must be met for Incremental and Differential backups to work properly:

  1. Both Incremental and Differential backups require that a Full Backup be completed first.
  2. You must retain your most recent Full Backup at all times for a complete restore.
  3. Use of Incremental and Differential backups will create dependencies between backup runs.
  4. File System backups can be done as Incremental backups, Differential backups, or both.
    1. Backups of other data types, like certain applications, may not support Incremental and/or Differential backups.
    2. System State backups can be run as Full Backups only.
  5. No matter which you choose, we recommend you perform a regular Full Backup.

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Differential Backups

A Differential backup will back up any data that has changed since the last Full Backup. Differential backups will start small but grow in size for each subsequent backup, because they contain all changed data since the last Full backup. Each one will be larger than the one before it, until you perform the next Full Backup. The rate of growth depends on the amount of data you change. For many, it is slow. For others, quite fast.

Performing a new Full Backup will reset the Differentials back to their smallest size.

To perform a full restore of all data, you will need the most recent Full Backup and the most recent Differential backup.

Incremental Backups

An Incremental backup will back up any data that has changed since the last backup, be it Full, Differential, or Incremental.

This means that all Incremental Backups will be small in size, compared to a Full backup. There is no growth in file size over time, unlike Differential backups. The exact size of the backup depends entirely on how much data changes between backups.

A full restore of all data involving Incremental backups needs:

  1. The most recent Full backup.
  2. The most recent Differential backup, if one was done.
  3. Every Incremental backup that was taken since the most recent Full or Differential backup.

Which is Better

Incremental backups are generally much smaller in size than differential backups, but they can make the restore process slower over a period of time.

On the other hand, differential backups offer a good tradeoff between time to backup and time to restore.

To reap the benefits of both incremental and differential backups, you may combine both types in a single backup set. A backup set that mixes both incremental and differential backups may look like this:

  • Do a Full backup every month
  • Do Differential backups every week
  • Do Incremental backups every day

Note: You can select the predefined backup template for Monthly Full + Weekly Differential + Daily Incremental, from the Edit your backup schedule section.