On 02/02/2013 07:02 AM, harryxiyou wrote: [no need to cc me specifically, I read the list for a reason] [no need to add "[Libvirt]" to your subject line, the list already adds that automatically, making your messages come through with double tags: https://www.redhat.com/archives/libvir-list/2013-February/thread.html#00072] Yes, loading that snapshot XML with 'virsh snapshot-create $dom $file --disk-only' while $dom is active would do what you describe, by using the qemu 'blockdev-snapshot-sync' QMP command under the hood. By default, that snapshot XML will create /path/to/new as a qcow2 file, even if /path/to/old is a sheepdog volume. I'm not very familiar with sheepdog myself, but my impression is that sheepdog always forms the base element of a stack as used by qemu - there's no way to make qemu use a sheepdog volume that has /path/to/old as it's backing file with qemu managing /path/to/old. I don't know if sheepdog as a protocol supports internal snapshots; but if it does, then we still need support added to qemu to tell sheepdog to take an internal snapshot, then wiring up support in libvirt to use that new qemu command. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org