Comment 6 for bug 1417288

I looked a bit more into this and more and more get the impression that this particular setup has not and is not supported.

Ben, did snapshots with type volume storage definitions ever work for you? And the other question would be whether it is possible to convert the currents guests and the process of creating new guests to use the type=file format of storage definitions.

A bit more background: snapshots are only supported on file-backed disks. When defining a disk as type=volume, the internal structure that holds the disk stores both the volume name (type=volume) and the path (type=file) in the same source element. But all the code for snapshots assumes a local path in there. For type=volume this would require additional checking (since there are pools that do not contains file backed volumes) and re-direction (to resolve the volume name into a path). None of this is present even in the recent releases of libvirt. So it might be a restriction that has not been documented well.