[libvirt] vm snapshot multi-disk

[Marcus]

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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