Re: [libvirt-users] Live external snapshot coalescing

On 03/04/2013 12:18 PM, Skardal, Harald wrote: Correct - F18 shipped with libvirt 0.10.2 and qemu 1.2, but live blockcommit wasn't until libvirt 1.0.1 and qemu 1.3. fedora-virt-preview provides new enough alternatives. That's more of a fedora problem (and I see you reported it separately in a different email), so hopefully it gets fixed soon. Yeah, I still haven't finished the code to support offline blockcommit. I know what needs to happen (it is basically a sequence of 'qemu-img commit' commands under the hood); the problem is that exposing it means that libvirt will have to do long-running job management. With live blockcommit, qemu is doing the job management on libvirt's behalf, so that code was easier to write. At least offline coalescing is something you can do yourself, if you are willing to get dirty with qemu-img commands yourself, followed by any cleanup to tell libvirt how to correct its view of the world to account for the changes you did behind its back with qemu-img. Another thing we have not yet coded - right now, there is no interaction between the libvirt snapshot code and the libvirt block commit code, which means any blockcommit (or blockpull) that changes the backing file layout may leave inconsistent snapshot metadata around. If the bogus snapshot metadata is in the way, you can safely delete the metadata (virsh snapshot-delete --metadata $dom $name); or, you can go one step further and create your external snapshots without ever having libvirt track the metadata in the first place (virsh snapshot-create[-as] ... --no-metadata). Someday, when we _properly_ represent an entire backing chain for each <disk> element, then we will also make sure that any libvirt operation that alters a backing chain (snapshot-create, blockcopy, blockcommit, blockpull) also alters all references to that backing chain (domain xml and all snapshots of that domain). But that's a ways down the road. The libvirt snapshot listing is stale, so deleting the metadata for that snapshot is the right solution for now. No. While 'virsh snapshot-delete' without options refuses to work on external snapshots, 'virsh snapshot-delete --metadata' has been working since libvirt 0.9.5 or so. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org