VM Disks Support for oVirt Incremental Backup
Challenge
A backup job for an Oracle Linux Virtualization Manager and Red Hat Virtualization VM could not enable incremental backup support. One of the following warnings may occur:
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Unable to enable ovirt incremental backups for disk '':. Full scan backups will be performed. Please see KBxxxxx for more information
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Unable to create incremental backup: Cannot backup VM. Incremental backup is not supported.
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Unable to backup disks incrementally, using full scan backup.
This error specifically occurs when the disk is raw.
Solution
Here are the two most common causes of this issue and how to resolve them.
Cause 1: Incremental Backup Support is disabled at the system level
Incremental backup support may be disabled at the system level.
Solution:
- Connect to the ovirt-engine system via ssh
- Execute the following commands:
engine-config -s "IsIncrementalBackupSupported=true"
systemctl restart ovirt-engineCause 2: VM Disk created without Incremental Backup support
When creating a VM disk, if the option for 'Enable Incremental Backup' is not enabled, the disk will be created in RAW format and won't support incremental backups. After the disk has been created, the 'Enable Incremental Backup' option will be greyed out and cannot be enabled.
Solution:
There are two methods to resolve this limitation.
- (Recommended) Create a snapshot of the VM. Then, edit the disk and enable the Incremental Backup option.
Note: The snapshot must remain in place. If it is removed, the Incremental Backup option will become disabled. In the long term, you should rebuild the VM/disk to have Incremental Backup enabled on the disk at the time of creation. - Convert the disk from RAW to QCOW2
Review: KB4345: Converting Disk from RAW to QCOW2 to Allow For Incremental Backup
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