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 !

Best,
Yuanzhen


On Tue, Aug 5, 2014 at 6:30 PM, Eric Blake <eblake@redhat.com> wrote:
On 08/05/2014 03:54 PM, Yuanzhen Gu wrote:
> Hello folks,
>
> If I give command to take external disk-only live snapshot, such as
> # virsh snapshot-create-as vm1 snapshot_vm1 --disk-only
>
> will the guest OS be paused or suspend while the snapshot being taken?

The guest will temporarily pause, but the time that it remains paused
will be a fraction of a second.  In practice, it is no longer than the
time that the guest is paused when doing live migration.

--
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org