On 03/27/2014 04:48 PM, Jon Bernard wrote: > > One thing comes to mind: once volumes are quiesced, qemu-img could be > used directly to create the snapshot. In the case of iSCSI-attached > volumes, a remote snapshot command could be issued to create a snapshot. > Once all have completed the guest then thawed. > > For local volumes, using qemu-img seems cumbersome to me. I feel there > should be a libvirt call to handle at least the local volumes. virDomainSnapshotCreateXML already handles a snapshot of a subset of local volumes via qemu. The reason we are adding FSFreeze/FSThaw is to cater to situations where creating the snapshot via qemu is not feasible. But be aware that you generally must NOT use qemu-img on a disk that is in-use by qemu, as qemu may have pending changes to the image metadata that would cause qemu-img to misbehave. If a guest is live (even if paused or quiesced), the only safe things you can do to that guest are to backing files (which are read-only to qemu) or actions supported directly by qemu (and yes, we still need qemu to have a way to pivot to a new disk file if you have a way of doing a fast snapshot while the disk is quiesced but in a way different than how qemu does snapshots with qcow2 files). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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