Infrastructure

There doesn't seem to be a virt-group config like
https://github.com/gluster/glusterfs/blob/master/extras/group-virt.example
on the server, so the image-volume has some performance hits in the
guests.

At least that is my guess from the "Volume Option group=virt could not
be set on images" message and corresponding google search :-)

so can you double-check that there is /var/lib/glusterd/groups/virt
and if not create it and assign the corresponding group to the volume
please?