[libvirt-users] some problem with snapshot by libvirt

Hi,all,i am using libvirt to manage my vm,in these days i am testing the libvirt snapshot ,but meet some problem: the snapshot was created from this command: snapshot-create-as win7 --disk-only --diskspec vda,snapshot=external --diskspec hda,snapshot=no but when i tried to revert from the snapshot which created from the above command ,i got error below: virsh # snapshot-revert win7 1338041515 --force error: unsupported configuration: revert to external disk snapshot not supported yet version: virsh # version Compiled against library: libvir 0.9.4 Using library: libvir 0.9.4 Using API: QEMU 0.9.4 Running hypervisor: QEMU 1.0.93