Re: vm snapshot multi-disk

[Marcus <shadowsor@xxxxxxxxx>]

I'm guessing this is an issue with qemu, as the code indicates that libvirt relies on the qemu monitor when a vm is active, via  qemuMonitorDeleteSnapshot. If I'm barking up the wrong tree, someone please let me know. Otherwise I'll follow up with qemu-devel.

On Mon, Jul 13, 2015 at 2:42 PM, Marcus <shadowsor@xxxxxxxxx> wrote:

Oh, I almost forgot to mention the versions:

libvirt 1.2.8-16.0.1.el7_1.2.x86_64

qemu 2.1.2-23.el7_1.1.x86_64

Also, I'm unclear if the domain snapshot feature is orchestrated by libvirt, or something that is simply called into qemu to take care of. Please forgive me if this is a qemu issue.

On Mon, Jul 13, 2015 at 2:35 PM, Marcus <shadowsor@xxxxxxxxx> wrote:

Hi all,

    I've recently been toying with VM snapshots, and have ran into an issue. Given a VM with multiple disks, it seems a snapshot-create followed by a snapshot-delete will only remove the qcow2 snapshot for the first disk (or perhaps just the disk that contains the memory), not all of the disk snapshots it created. Is this something people are aware of? 

    In searching around, I found a bug report where snapshot-creates would fail due to the qcow2 snapshot ids being inconsistent. That looks like it is patched for 2.4 qemu (http://lists.nongnu.org/archive/html/qemu-devel/2015-03/msg04963.html), this bug would trigger that one by leaving IDs around that are inconsistent between member disks, but is not the same.

# virsh snapshot-create 7

Domain snapshot 1436792720 created

# virsh snapshot-list 7

 Name                 Creation Time             State

------------------------------------------------------------

 1436792720           2015-07-13 06:05:20 -0700 running

# virsh domblklist 7

Target     Source

------------------------------------------------

vda        /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/e4d6e885-1382-40bc-890b-ad9c8b51a7a5

vdb        /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/7033e4c6-5f59-4325-b7e0-ae191e12e86c

# qemu-img snapshot -l  /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/e4d6e885-1382-40bc-890b-ad9c8b51a7a5

Snapshot list:

ID        TAG                 VM SIZE                DATE       VM CLOCK

1         1436792720             173M 2015-07-13 06:05:20   00:01:10.938

# qemu-img snapshot -l  /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/7033e4c6-5f59-4325-b7e0-ae191e12e86c

Snapshot list:

ID        TAG                 VM SIZE                DATE       VM CLOCK

1         1436792720                0 2015-07-13 06:05:20   00:01:10.938

# virsh snapshot-delete 7 1436792720

Domain snapshot 1436792720 deleted

# qemu-img snapshot -l  /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/e4d6e885-1382-40bc-890b-ad9c8b51a7a5

# qemu-img snapshot -l  /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/7033e4c6-5f59-4325-b7e0-ae191e12e86c

Snapshot list:

ID        TAG                 VM SIZE                DATE       VM CLOCK

1         1436792720                0 2015-07-13 06:05:20   00:01:10.938

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