Differential vs Incremental backups: Why should you care?
by Eric Lemarque, on Oct 28, 2013 10:50:49 AM
Differential and Incremental backups are called “Intelligent” or "smart" backups because they reduce the amount of time required to back up and the disk space required to do so. Only a small percentage of information on a computer changes on a daily basis, so running a full backup every day can result in wasted time and disk space. Differential and Incremental backups allow you to only backup changes in different ways; saving time, storage space and money. Keep reading to learn more about the differences between Differential vs Incremental backups and why you should care about them.
Editor’s Note: Most backup companies recommend a full backup weekly as part of an overall backup/data-integrity plan. Additionally, Full backups are also recommended if there are major changes to a system (e.g. a change in Operating Systems, an update in software or new software installation).
Full backups: Backup up the entire set of data selected, require the most disk space, and are the most time-consuming, yet simplest form of backup.
Differential backups: Differential backups are based on the last full backup performed and backup all changes since the last Full backup was performed.
Incremental backups: Incremental backups are based on the last backup performed and backup only the changes since that last backup (Full or Differential).
With Incremental backups, after the source data is copied in full,
any new backups only contain new or updated data since the last backup.
With Differential backups, after the source data is copied in full,
any new backups, contain a compilation of new or updated data since the last full backup.
Incremental and Differential backups were both designed to allow you to backup only files that have changed, although they differ on which files are selected. Incremental backups will back up any changes you have made since your last backup (regardless of type), whereas Differential backs up all of the changes since your last Full backup.
In the illustration above, you can see that a differential backup is similar to an incremental backup in that both start with a full backup. Once the full backup is performed there are key differences between incremental vs differential backups.
For example, if you were to do a full backup on Monday and then you perform differential backups the rest of the week. On Tuesday, the backup would contain only the data that had changed since Monday. On Wednesday, the backups would again contain the data that changed since Monday when you had performed your full backup. Whereas, if you were doing incremental backups, on Wednesday, you would only be backing up changes since Tuesday.
While it is easy to see that the file backup size and thus storage requirements and backup window would be smaller for incremental backups, the upside to differential backups is in the reduced restore times. With differential backups, you would only use two data sets to restore, your last full backup plus the most current differential backup.
For businesses that need to back up data multiple times per day due to the nature of their business, incremental backups offer the smallest, fastest backup speeds allowing for more granularity when it comes to recovery. If you are only backing up once per day, then you may lose a whole day of data when it comes time to recover.
As part of your overall backup strategy, the option to select an Incremental backup a or Differential backup can help manage your data storage and backup job speed. For more detailed information relating to how Differential or Incremental backups differ, please see our FAQ: The differences between a Full, Incremental, or Differential backup
Selecting the Right Backup Policy
Choosing the right setup of incremental vs differential backups for your backup policy will depend on your space, time, and the level of data protection desired. For more information on PC backup, view post on understanding your PC backup software needs.