Hello again,I'm not sure which update did the trick but live migrations are now working again.
Unfortunately now all thin provisioned image files (qcow2) are copied as full allocated, just as reported here: https://bugzilla.redhat.com/show_bug.cgi?id=817700 and https://bugs.launchpad.net/qemu/+bug/1449687. This worked before, but this is another problem and I think this bug can be closed.
Best Regards Ansgar
