On 04/29/2015 10:09 AM, Andreas Buschmann wrote: If you use qcow2 backing chains for thin provisioning, as in: base.qcow2 <- active.qcow2 then --copy-storage-all copies the entire disk over to the destination (both base.qcow2 and active.qcow2 contents), while --copy-storage-inc copies only active.qcow2 (and assumes you have manually copied base.qcow2 in some other means - since it is read-only, it won't change from the last migration, and there are some storage arrays where you can very efficiently copy files around). Thus, --copy-storage-inc can be MUCH faster if active.qcow2 represents a small delta in relation to base.qcow2. The above conversation is independent of NBD snapshots, which are something else altogether. The active layer has to be able to have backing images (qcow2 is the most common format that has this property, but other formats like qed also work). The backing file can be any format. Raw files can't have backing images, so there is nothing incremental to be copied. No. It requires existing backing files. 'virsh snapshot-create' for creating external snapshots is one way to create backing file chains, but you can have backing chains without using libvirt snapshot chains to create them. Yes. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org