1536: Difference between Full, Incremental and Differential Backup

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In what way full, differential and incremental backups differ from each other

Description

A full backup is a self-sufficient backup containing all data chosen for backup. You do not need access to any other backup to recover the data from a full backup

An incremental backup contains all changes that have been made since the latest incremental or full backup was created. If one full backup and several incremental were created, all of these backups must be saved in the same folder so that you will be able to restore the data. If one of incremental backups or a full backup is deleted, there is no way to restore the set, since all backups are dependent on each other.

A differential backup contains all changes that have been made after the full backup creation. You need access to the corresponding full backup to recover the data from a differential backup

So, If your objective is to reduce backup size and backup time, then the best strategy would be to create incremental backups. On the other hand, if you want to increase backup reliability, by not having to rely on a chain of incremental backups, then differential backups would be the best solution.

Here is a graphical representation of the differences between full, incremental and differential backups:

    
Click the pictures to enlarge

Single-file backup format (always incremental backup)
A new backup format, in which the initial full and subsequent incremental backups are saved to a single .tib file, instead of a chain of files. This format leverages the speed of the incremental backup method, while avoiding its main disadvantage–difficult deletion of outdated backups. The software marks the blocks used by outdated backups as "free" and writes new backups to these blocks. This backup format is available in Acronis Backup 12.5 and Acronis Backup Cloud.
 

More information

An incremental or differential backup created after the disk is defragmented might be considerably larger than usual. This is because the defragmentation program changes file locations on the disk and backups reflect these changes. Therefore, it is recommended that you re-create a full backup after disk defragmentation.

Technically there is no limit on the number of incremental/differential backups in a chain. However, since one invalid incremental backup makes all consequent incremental backups inaccessible, it is recommended to create a  new full backup after several incrementals and start a new chain.

See also https://www.acronis.com/en-us/articles/incremental-differential-backups/

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