[libvirt] vm snapshot multi-disk

Marcus shadowsor at gmail.com
Tue Jul 14 05:25:51 UTC 2015


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 at gmail.com> 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 at gmail.com> 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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