[ovirt-users] Can't remove snapshot

[Adam Litke]

On 18/02/16 10:37 +0100, Rik Theys wrote:
>Hi,
>
>On 02/17/2016 05:29 PM, Adam Litke wrote:
>> On 17/02/16 11:14 -0500, Greg Padgett wrote:
>>> On 02/17/2016 03:42 AM, Rik Theys wrote:
>>>> Hi,
>>>>
>>>> On 02/16/2016 10:52 PM, Greg Padgett wrote:
>>>>> On 02/16/2016 08:50 AM, Rik Theys wrote:
>>>>>>  From the above I conclude that the disk with id that ends with
>>>>> Similar to what I wrote to Marcelo above in the thread, I'd recommend
>>>>> running the "VM disk info gathering tool" attached to [1].  It's the
>>>>> best way to ensure the merge was completed and determine which image is
>>>>> the "bad" one that is no longer in use by any volume chains.
>>>>
>>>> I've ran the disk info gathering tool and this outputs (for the affected
>>>> VM):
>>>>
>>>> VM lena
>>>>     Disk b2390535-744f-4c02-bdc8-5a897226554b
>>>> (sd:a7ba2db3-517c-408a-8b27-ea45989d6416)
>>>>     Volumes:
>>>>         24d78600-22f4-44f7-987b-fbd866736249
>>>>
>>>> The id of the volume is the ID of the snapshot that is marked "illegal".
>>>> So the "bad" image would be the dc39 one, which according to the UI is
>>>> in use by the "Active VM" snapshot. Can this make sense?
>>>
>>> It looks accurate.  Live merges are "backwards" merges, so the merge
>>> would have pushed data from the volume associated with "Active VM"
>>> into the volume associated with the snapshot you're trying to remove.
>>>
>>> Upon completion, we "pivot" so that the VM uses that older volume, and
>>> we update the engine database to reflect this (basically we
>>> re-associate that older volume with, in your case, "Active VM").
>>>
>>> In your case, it seems the pivot operation was done, but the database
>>> wasn't updated to reflect it.  Given snapshot/image associations e.g.:
>>>
>>>  VM Name  Snapshot Name  Volume
>>>  -------  -------------  ------
>>>  My-VM    Active VM      123-abc
>>>  My-VM    My-Snapshot    789-def
>>>
>>> My-VM in your case is actually running on volume 789-def.  If you run
>>> the db fixup script and supply ("My-VM", "My-Snapshot", "123-abc")
>>> (note the volume is the newer, "bad" one), then it will switch the
>>> volume association for you and remove the invalid entries.
>>>
>>> Of course, I'd shut down the VM, and back up the db beforehand.
>
>I've executed the sql script and it seems to have worked. Thanks!
>
>>> "Active VM" should now be unused; it previously (pre-merge) was the
>>> data written since the snapshot was taken.  Normally the larger actual
>>> size might be from qcow format overhead.  If your listing above is
>>> complete (ie one volume for the vm), then I'm not sure why the base
>>> volume would have a larger actual size than virtual size.
>>>
>>> Adam, Nir--any thoughts on this?
>>
>> There is a bug which has caused inflation of the snapshot volumes when
>> performing a live merge.  We are submitting fixes for 3.5, 3.6, and
>> master right at this moment.
>
>Which bug number is assigned to this bug? Will upgrading to a release
>with a fix reduce the disk usage again?

See https://bugzilla.redhat.com/show_bug.cgi?id=1301709 for the bug.
It's about a clone disk failure after the problem occurs.
Unfortunately, there is not an automatic way to repair the raw base
volumes if they were affected by this bug.  They will need to be
manually shrunk using lvreduce if you are certain that they are
inflated.


-- 
Adam Litke