On Mon, Jun 28, 2021 at 11:07 AM Laurent Duparchy <[email protected]> wrote:
>
> Hi,
>
> Thanks you for your response.
>
> I'm new to ovirt / LVM (Oracle flavor). I'm wondering why LVM snapshots don't
> have the "s" attribute. ..
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)
> ( I noticed it while looking for the best way to backup the VMs to tape.
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.
> We must have an offline & out-of-band backup to tape which is part of our
> "Disaster Recovery Plan".
> At the moment a (most simple) "dd" of the entire Volume Group seems OK.
> Nevertheless checking if more granular is possible...
> Keeping things simple being a goal. )
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
> Laurent Duparchy
> ESRF - The European Synchrotron
> MIS Group
> 04 76 88 22 56 / 06 71 10 38 40
>
> Nir Soffer wrote on 21/06/2021 21:35:
>
> On Mon, Jun 21, 2021 at 10:29 PM <[email protected]> wrote:
>
> Hi,
> What are the internal commands used to clone LVM partitions ?
>
> Are you sure this is the right mailing list?
>
> (you can simply indicate me the source code where this is done)
>
> If you mean how we copy disks lvm based disks (e.g. on FC/iSCSI storage
> domain),
> we use this:
> https://github.com/oVirt/vdsm/blob/4f728377f6cd6950035a7739014737789a4d6f14/lib/vdsm/storage/qemuimg.py#L232
>
> Most flows uses this API for copying disks:
> https://github.com/oVirt/vdsm/blob/master/lib/vdsm/storage/sdm/api/copy_data.py
>
> Nir
>
>
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