Retention Rules - ACRONIS BACKUP AND RECOVERY 10 ADVANCED SERVER SBS EDITION - UPDATE 3 User Manual


the pattern starts with a full backup since the very first backup cannot be incremental
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the scheme forces every backup level to keep only the most recent backup, other backups from
the level have to be deleted; however backup deletion is postponed in cases where the backup is
a base for another incremental or differential one
 an old backup on a level is kept until a new backup has been successfully created on the level.
The table shows the pattern for the five-level backup scheme. The pattern consists of 16 sessions.
As a result of using incremental and differential backups the situation may arise when an old backup
deletion must be postponed as it still is a base for other backups. The table below indicates the case
when deletion of full backup (E) created at session 1 is postponed at session 17 until session 25
because the differential backup (D) created at session 9 is still actual. In the table all cells with
deleted backups are grayed out:
Differential backup (D) created at session 9 will be deleted at session 25 after creation of a new
differential backup is completed. This way, a backup archive created in accordance with the Tower of
Hanoi scheme by Acronis sometimes includes up to two additional backups over the classical
implementation of the scheme.
For information about using Tower of Hanoi for tape libraries, see Using the Tower of Hanoi tape
rotation scheme (p. 145).

2.7 Retention rules

The backups produced by a backup plan make an archive. The two retention rules described in this
section enable you to limit the archive size and set the lifetime (retention period) of the backups.
The retention rules are effective if the archive contains more than one backup. This means that the
last backup in the archive will be kept, even if a retention rule violation is detected. Please do not try
to delete the only backup you have by applying the retention rules before backup. This will not work.
Use the alternative setting Clean up archive > When there is insufficient space while backing up (p.
207) if you accept the risk of losing the last backup.
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