[ovirt-users] Cannot remove snapshot

[Nicolas Ecarnot]

Hello,

oVirt 3.6.7.5-1
I'm trying to remove a snapshot in a cold way (VM shut down).
It is failing, and VDSM is telling :

4f1588f3-ae2d-4702-b7e1-4ef53b5b5a1d::DEBUG::2017-11-17 
13:04:11,448::lvm::290::Storage.Misc.excCmd::(cmd) SUCCESS: <err> = ' 
WARNING: lvmetad is running but disabled. Restart lvmetad before 
enabling it!\n'; <rc> = 0
4f1588f3-ae2d-4702-b7e1-4ef53b5b5a1d::DEBUG::2017-11-17 
13:04:11,456::lvm::462::Storage.LVM::(_reloadlvs) lvs reloaded
4f1588f3-ae2d-4702-b7e1-4ef53b5b5a1d::DEBUG::2017-11-17 
13:04:11,456::lvm::462::Storage.OperationMutex::(_reloadlvs) Operation 
'lvm reload operation' released the operation mutex
4f1588f3-ae2d-4702-b7e1-4ef53b5b5a1d::ERROR::2017-11-17 
13:04:11,457::image::1302::Storage.Image::(merge) Unexpected error
Traceback (most recent call last):
   File "/usr/share/vdsm/storage/image.py", line 1293, in merge
     sdDom, srcVolParams, volParams, reqSize, chain)
   File "/usr/share/vdsm/storage/image.py", line 1039, in 
_baseCowVolumeMerge
     unsafe=False, rollback=True)
   File "/usr/share/vdsm/storage/volume.py", line 278, in rebase
     raise se.MergeSnapshotsError(self.volUUID)
MergeSnapshotsError: Error merging snapshots: 
('4a8c17aa-5882-45a1-8a6e-40db39ed06ca',)

I read this : https://bugzilla.redhat.com/show_bug.cgi?id=1069610 , 
hoping I could find some workaround. But I couldn't.

If there is no abvious workaround, would there be other ways like :
- find the bare logical volume, shut down the VM, and play with low 
level qemu-img commands. I think I knwn how to do that, but I'm worried 
the oVirt database won't be in sync once I've removed the snapshot

or

- export the VM then re-import, if this is related to some LV space 
missing. Then removing the snapshot the usual way.

Any advice (apart the obvious upgrade-to-4.X-sir)?

-- 
Nicolas ECARNOT