et aussi l'épisode 1 http://kashyapc.wordpress.com/2011/10/04/snapshotting-with-libvirt-for-qcow2-images/
http://www.redhat.com/archives/libvirt-users/2013-October/msg00018.html
http://www.azertech.net/content/kvm-qemu-qcow2-qemu-img-and-snapshots
