After looking into a qemu a bit, I believe the snapshot operation on the disk in oVirt is not a live snapshot, because the guest VM will be paused by qemu when the snapshot is undergoing. That is what qemu monitor command "snapshot_blkdev" does and VDSM depends on that command in low level. Most likely, the pausing time is non-trival for a normal snapshot. On 2012-6-29 0:37, Itamar Heim wrote:
On 06/28/2012 09:20 AM, Eric Blake wrote:
On 06/28/2012 07:07 AM, Dave Allan wrote:
On Thu, Jun 28, 2012 at 06:34:25AM -0400, Itamar Heim wrote:
On 06/28/2012 04:40 AM, Winfried de Heiden wrote:
Hi all,
It seems live snapshot is available in the Fedora 17 qemu-kvm. On my laptop with kvm, virt-manager, libvirt, virsh etc. I created a virtual machine and tried to make a live snapshot:
virsh # snapshot-create RHEL55_NTP Domain snapshot 1340871802 created
That's a system-checkpoint snapshot, because you didn't use --disk-only. When you say 'live snapshot' were you intending the fast operation of just a disk snapshot (via the 'transaction' or 'blockdev-snapshot-sync' monitor command) or the slow operation of a checkpoint (via the 'savevm' monitor command)?
[root@kvm ~]# rpm -qf `which qemu-kvm` qemu-system-x86-1.0-17.fc17.x86_64
[wdh@laptop-winfried ~]$ rpm -qf `which qemu-kvm` qemu-system-x86-1.0-17.fc17.x86_64
This qemu does not support the 'transaction' monitor command, so libvirt has to fall back to the non-atomic 'blockdev-snapshot-sync', or else give up because of missing functionality.
dave - who can help us elaborate on this libvirt error: reuse is not supported with this QEMU binary
this is the relevant error coming from libvirt. maybe fedora 17 qemu-kvm does not have live snapshot support?
Thread-306::ERROR::2012-06-27 12:46:40,178::libvirtvm::1782::vm.Vm::(snapshot) vmId=`ef978066-09c8-40aa-8e0b-4accfacc15bd`::Unable to take snapshot Traceback (most recent call last): File "/usr/share/vdsm/libvirtvm.py", line 1780, in snapshot libvirt.VIR_DOMAIN_SNAPSHOT_CREATE_REUSE_EXT))
OK, so this is a case of VDSM driving a different use of the API than what you did with your virsh command line. VDSM is attempting to do the equivalent of 'virsh snapshot-create --disk-only --reuse-ext', but because your qemu doesn't support the 'transaction' command, libvirt can't make qemu do what VDSM wants. Basically, the 'blockdev-snapshot-sync' command in qemu 1.0 lacks the ability to reuse qcow2 metadata already present in the file pre-created by VDSM; this wasn't added until the 'transaction' command of qemu 1.1.
ok, i guess the question is then when qemu 1.1 is expected in fedora _______________________________________________ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
-- Shu Ming <shuming@linux.vnet.ibm.com> IBM China Systems and Technology Laboratory