Reversed Incremental – Animation of Method and Retention

KB ID:
1933
Product:
Veeam Backup & Replication
Version:
7.x
Published:
Last Modified:
2014-09-30
KB Languages:
FR

Purpose

This article is intended to document how Reversed Incremental works, and how it’s retention is enforced.

Solution

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Reversed Incremental Backup Method
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Reversed incremental backup implies that during the first run of a backup job a full backup of a VM is created. VM data is copied block by block, compressed at an appropriate compression level, and stored in a resulting full backup file (.vbk). All subsequent backups are incremental (that is, Veeam Backup & Replication copies only those data blocks that have changed since the last job run). During reverse incremental backup, Veeam Backup & Replication “injects” changes into the .vbk file to rebuild it to the most recent state of the VM. It also creates a reversed incremental backup file (.vrb) containing data blocks that are replaced when the full backup file is rebuilt. Therefore, the most recent restore point is always a full backup, and it gets updated after every backup cycle.
 
User-added image

 
Within this animation the lettered squares represent blocks on a disk.
 
This backup method lets you perform forever-incremental backup and save disk space as you have to store only one full restore point on the backup repository. If the number of restore points allowed by the retention policy is exceeded, Veeam Backup & Replication will simply delete the oldest reversed increment.
 
Note: Due to the manner in which the full restore point is updated during the job run by “injecting” changed blocks, then reading out the replaced blocks and writing those replaced blocks in to a rollback; The job will generate 3 times as much I/O on the target storage. This I/O load can be very heavy, and it is advised to ensure that the destination storage has the IOPS to allow for acceptable backup performance.
 
Reversed incremental backup enables you to immediately restore a VM to the most recent state without extra processing, because the most recent restore point is a full backup file. If you need to restore a VM to a particular point in time, Veeam Backup & Replication will apply the required .vrb files to the .vbk file to get to the required restore point.
 
User-added image

 
Within this animation the lettered squares represent blocks on a disk.
 
For more information please review the follow portions of the Help Center:
http://helpcenter.veeam.com/backup/70/vsphere/reversed_incremental_backup.html
http://helpcenter.veeam.com/backup/70/vsphere/retention_reversed.html
http://helpcenter.veeam.com/backup/70/vsphere/retention_separate_vms.html



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