Re: [libvirt] libvirt external disk-only snapshot will pause the VM?
yes, I got your point, thanks very much Eric.
If I want to take a distributed snapshot, which need pause all the VMs and
then take snapshot, how can I control the pause for all the VMs?
Is there only way that I turn to freeze/thaw functions?
and freeze/thaw only for file systems, not for the whole guest, am I right?
Thanks a lot!
Best,
Yuanzhen
On Wed, Aug 6, 2014 at 11:35 AM, Eric Blake <eblake(a)redhat.com> wrote:
On 08/06/2014 08:36 AM, Yuanzhen Gu wrote:
[please don't top-post on technical lists]
> Thanks very much Eric! This is exactly what I guessed, I just wondering
> where I could find this piece of code and control the the pause time of
> guest, while the snapshot being taken? thanks !
Actually, for new enough qemu (one with the 'transaction' QMP command),
or for a guest where only one disk is being snapshotted, there is no
pause required. See qemuDomainSnapshotCreateDiskActiveExternal in
src/qemu/qemu_driver.c. When a pause is required, it is only for the
fraction of a second required to issue a followup qemu QMP command to
resume the guest, so there is no need for a knob to control the pause
time (it is as already as fast as possible).
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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