On Tue, Jan 26, 2016 at 12:59:00 +0300, Alexander Burluka wrote:
On 01/25/2016 04:16 PM, Daniel P. Berrange wrote:
For example, we want to store suspended state of VM. I'm aware that some other careless application dealing with libvirt may erase metadata section and info about additional snapshot data will be lost. What do you mean by suspended state of the VM ? Are you referring to
On Mon, Jan 25, 2016 at 02:55:30PM +0300, Alexander Burluka wrote: the VM memory & device state ? If so, I think that something that should be explicitly represented in the API, not a opaque blob. We distinguish paused and suspended to disk domain states. For suspend to disk we are using virDomainSaveFlags API call and stop domain.
So you are saving the domain to a file which is out of libvirt's control and your management app (I guess) tracks the file for each domain.
This API call stores VM memory and device states to some file. If user then calls virDomainSnapshotCreateXML, the resulted snapshot lacks VM memory and device states because it looks like domain is stopped and it is not aware about state file. Thus, switch to this snapshot does not work as expected.
It is the responsibility of your management app to associate the state files with snapshots and to properly restore them when switching between snapshots. I don't think libvirt should behave as a general purpose database for management apps. The situation would be quite different if you used virDomainManagedSave to save its state. In this case, it's libvirt's responsibility to be aware of a saved state when creating/reverting snapshots. And currently libvirt doesn't handle this correctly. Jirka