On Mon, Jun 28, 2021 at 11:07 AM Laurent Duparchy <duparchy(a)esrf.fr&gt; wrote: We don't use LVM snapshots for VM disks. oVirt snapshots are using qcow2 logical volumes per VM snapshots. For example VM can start with one logical volume: /dev/vgname/lv-1 When you create a snapshot in engine, ovirt creates new logical volume: /dev/vgname/lv-2 And creates a qcow2 image using /dev/vgname/lv-1 as the backing file: /dev/vgname/lv-1 <- /dev/vgname/lv-2 (top) The best way with oVirt 4.4 is to use incremental backup, but you are likely using 4.3. There are several backup solutions that use snapshots to create incremental backup. This is more complex and less efficient but it should be available for your version. Keeping things simple backup at the storage side at the LUN level is probably the simplest way. It may also be the most efficient way depending on the storage capabilities, for example if your storage supports thin provisioning. But note that backup in storage level can create inconsistent backup, so starting a VM after restore may require running fsck. Using snapshots or incremental backup should generally avoid this issue if the VMs have qemu-guest-agent. Nir

On Tue, Jun 29, 2021 at 9:09 AM Laurent Duparchy <duparchy(a)esrf.fr&gt; wrote: ... Sure, keeping many snapshots is not recommended. You should not treat snapshots as long term backup, only as a temporary state to make it easy to revert changes in the vm. It makes sense to always keep one snapshot for backup purposes. Backup applications using snapshots use this algorithm: Day 1: 1. Create temporary snapshot (e.g. backup-1) 2. Backup snapshot backup-1 (e.g. using image transfer API) Day 2: 1. Create temporary snapshot (e.g. backup-2) 2. Backup snapshot backup-2 3. Delete snapshot backup-1 Day N: 1. Create temporary snapshot (e.g. backup-N) 2. Backup snapshot backup-N 3. Delete snapshot backup-(N-1) To download snapshot you can use this example: https://github.com/oVirt/ovirt-engine-sdk/blob/sdk_4.3/sdk/examples/downl... The example is not very good, and it downloads all snapshots instead of one but you can use it as an example how to create a transfer for disk snapshot. virt-v2v supports converting to format="qcow2" sparse=True. This should work with ovirt 4.3, but there is no way to use these options from the UI. If you convert in two steps: - from oracle vm to local file - from local file to ovirt and if you have recent enough virt-v2v, you should be able to choose the image format "qcow2" and allocation "sparse". -oa <sparse|preallocated> Set output allocation mode -of <raw|qcow2> Set output format One issue with virt-v2v is that it always allocates entire disk, even when using sparse disk, since it does not how to estimate the size of the disk: https://github.com/libguestfs/virt-v2v/blob/62c493e314f2d50db54079cd90c0d... To shrink the disk size to optimal size, you can reduce the disk after the import: https://github.com/oVirt/ovirt-engine-sdk/blob/master/sdk/examples/reduce... I think the simplest way to do this on 4.3 is to create a template from the vm, and choose qcow2 disk format. When the template is ready, you can create the vm back from the template, and delete the template. This requires downtime during the conversion. In 4.4. you can create a template from a snapshot to avoid the downtime. We are working on a disk conversion feature for 4.4.9, @Benny Zlotnik can add more info. Nir