Re: [libvirt] suggestions on snapshotting testing

On 05/14/2012 11:26 PM, Kashyap Chamarthy wrote: This documents the lower-level commands exposed by qemu, but not necessarily how libvirt uses them. I made that page prior to integrating the code for live disk snapshots, but have not maintained it since, so it might be a bit out of date with how things have changed in the meantime, but hopefully still relatively accurate. That page is live based on libvirt.git, and should be up-to-date with the current implementation; although I would welcome improvements for additional things to mention. Do you have specific scenarios in mind? Propose a problem that you think a snapshot would help, then ask questions on which APIs you would use to solve that problem. Do you understand the difference between the various snapshot flavors? There's several orthogonal issues to be aware of, although not all combinations are supported. system checkpoint: VM state and disk state 'virsh snapshot-create' disk only: just disk state 'virsh snapshot-create --disk-only' VM state only: 'virsh save' - I'd really like to make this a special case of 'virsh snapshot-create', but it needs more work online: taken from a running VM offline: taken from an offline VM live: online, plus the additional guideline that the VM continues running after the snapshot is taken, preferably with minimum downtime internal: requires qcow2, qemu stores VM state and disk state inside the qcow2 image, libvirt stores only an xml file tracking the state relation (qemu 'savevm' command) external: create a new file, possible for VM state (qemu 'migrate' to file) and disks (qemu 'transaction:blockdev-snapshot-sync') I'm sure additional tests would be welcome; perhaps libvirt-TCK would be a good place to add such tests. But I'm not quite sure what you plan to do, or which aspects you plan to test, without more details; I'll try to be responsive to any questions you have regarding specifics of any sequence you are trying to do. -- Eric Blake eblake(a)redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org