[ClusterLabs] Antw: snapshoting of running VirtualDomain resources - OCFS2 ?

Lentes, Bernd bernd.lentes at helmholtz-muenchen.de
Wed Mar 14 08:19:55 EDT 2018

----- On Mar 14, 2018, at 11:54 AM, Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de wrote:

> Hi!
> IMHO the only clean solution would be this procedure:
> 1) pause the VMs and cause them to flush their disk buffers, or at least make
> sure the writes of the VM guest arrived at the VM host's buffers
> 2) Cause the VM host filesystem buffers to be flushed to the disk (i.e.: LV)
> 3) Make a snapshot of the LV on the host
> 4) Unpause the VM guest
> 5) backup the LV snapshot on the host
> 6) delete the LV snapshot on the host
> Truely cool would be a solution where a snapshot created inside the VM is
> abailable as a snapshot on the host; then you could skip most steps.
> Regards,
> Ulrich


IIRC i can't make a snapshot of a clustered lv. This is what i found:

"Snapshotting is a problem. As Zdenek said, you have to set the other
nodes to inactive and then set the current host node's LV to
'exclusive'. Trick I found though was that you can't mark it as
exclusive while it's ACTIVE, and you can't make the LV inactive while
it's hosting a VM... So in practical terms, snapshotting clustered LVs
is not feasible." by Digimer.

That's why i'm thinking about OCFS2 for the snapshot. With qemu-img or virsh
i didn't find a solution without shutting down the guest.


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