Hey
When I want to take a snapshot for a Domain by using virDomainSnapshotCreateXML. The Error as below happen:

libvir: QEMU error : Requested operation is not valid: Disk '/var/lib/libvirt/images/fedora-qcow.qcow2' does not support snapshotting

The snapshot Configuration is :
<domainsnapshot>
  <description>Snapshot of OS install and updates</description>
  <disks>
    <disk name='/var/lib'>
      <source file='/var/lib-snapshot'/>
    </disk>
    <disk name='vdb' snapshot='no'/>
  </disks>
</domainsnapshot>

And /var/lib/libvirt/images/fedora-qcow.qcow2 is the disk for the domain (use qemu-img to create). And I had tried another Disk format
(*.img), but the error still happen. how can i deal with this error??

PS:qemu version is 0.14 & libvirt version is 0.9.4.  Pls help.   :-(