25 Copyright © Acronis International GmbH, 2002-2015
3.5 Full, incremental and differential backups
Acronis Backup provides the capability to use popular backup schemes, such as
Grandfather-Father-Son and Tower of Hanoi, as well as to create custom backup schemes. All backup
schemes are based on full, incremental and differential backup methods. The term "scheme" in fact
denotes the algorithm of applying these methods plus the algorithm of the archive cleanup.
Comparing backup methods with each other does not make much sense because the methods work
as a team in a backup scheme. Each method should play its specific role according to its advantages.
A competent backup scheme will benefit from the advantages of all backup methods and lessen the
influence of all the methods’ shortcomings. For example, weekly differential backup facilitates
archive cleanup because it can be easily deleted along with the weekly set of daily incremental
backups depending on it.
Backing up with the full, incremental or differential backup method results in a backup (p. 236) of the
corresponding type.
Full backup
A full backup stores all data selected for backup. A full backup underlies any archive and forms the
base for incremental and differential backups. An archive can contain multiple full backups or consist
of only full backups. A full backup is self-sufficient - you do not need access to any other backup to
recover data from a full backup.
It is widely accepted that a full backup is the slowest to do but the fastest to restore. With Acronis
technologies, recovery from an incremental backup may be not slower than recovery from a full one.
A full backup is most useful when:
you need to roll back the system to its initial state
this initial state does not change often, so there is no need for regular backup.
Example: An Internet cafe, school or university lab where the administrator often undoes changes
made by the students or guests but rarely updates the reference backup (in fact, after installing
software updates only). The backup time is not crucial in this case and the recovery time will be
minimal when recovering the systems from the full backup. The administrator can have several
copies of the full backup for additional reliability.
Incremental backup
An incremental backup stores changes to the data against the latest backup. You need access to
other backups from the same archive to recover data from an incremental backup.
An incremental backup is most useful when:
you need the possibility to roll back to any one of multiple saved states
the data changes tend to be small as compared to the total data size.
It is widely accepted that incremental backups are less reliable than full ones because if one backup
in the "chain" is corrupted, the next ones can no longer be used. However, storing multiple full
backups is not an option when you need multiple prior versions of your data, because reliability of an
oversized archive is even more questionable.
Example: Backing up a database transaction log.
