Gluster users - Feb 2015 - error creating volume in qemu storage pool

I want to create a kvm/qemu VM on gluster (two servers, one brick on
each, replicated). Fedora 21, gluster 3.5.3.

I can create a gluster storage pool from a third machine (also Fedora
21) using virt-manager. But when creating a volume in the pool, I get
"Libvirt version does not support storage cloning".

What does it mean?

-- 
Glenn Holmer (Linux registered user #16682)
"After the vintage season came the aftermath -- and Cenbe."