Comment 14 for bug 1334398

Thought I'd add the below.

I just created a simple test[1] which creates an external live snapshot[2] of a libvirt guest (with versions affecting the gate -- libvirt 1.2.2 and QEMU 2.0 on Fedora 20), by executing the below command in a loop of 100 (I also tested for 1000, it ran just fine too). I ran the script for 3 virtual machines in parallel.

$ virsh snapshot-create-as --domain $DOMAIN \
    --name snap-$i \
    --description snap$i-desc \
    --disk-only \
    --diskspec hda,snapshot=external,file=$SNAPSHOTS_DIR/$DOMAIN-snap$i.qcow2 \
    --atomic

Result of a 100 loop run would be an image with a backing chain of 100 qcow2 images[3].

The above script just creates a snapshot, nothing more. Matt Riedemann pointed out on #openstack-nova that on Gate there could be others tests running concurrently that could be doing things like suspend/resume/rescue, etc.

  [1] https://github.com/kashyapc/ostack-misc/blob/master/libvirt-live-snapshots-stress.sh
  [2] "external live snapshot "meaning: Every time you take a snapshot, the current disk becomes a (read-only) 'backing file' and a new qcow2 overlay is created to track the current 'delta'.
  [3] http://kashyapc.fedorapeople.org/virt/guest-with-backing-chain-of-100-qcow2-images.txt