Cause: 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.
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 using the qemu-img utility.
Please use official documentation
This method is not recommended as the conversion process can be time-consuming, and there is a risk of data loss.