[libvirt-users] QEMU IMG vs Libvirt block commit

[Erlon Cruz]

Just following up this to who, somehow hit this problem in the future...
What happens here is that when libvirt create the snapshots, it held the
disk/snapshots information in the domain XML. After I detach the volume,
and adding it again, Nova is not adding it the same way it was before
detaching, i.e, the backing files are not considered internally in the disk
XML representation. So, next step now is to know if its possible/how, to
attach a disk with external snapshots to a domain.


On Mon, Aug 1, 2016 at 11:43 AM, Erlon Cruz <sombrafam at gmail.com> wrote:

>
>
> On Thu, Jul 28, 2016 at 10:59 AM, Erlon Cruz <sombrafam at gmail.com> wrote:
>
>> Hi folks,
>>
>> I'm having a issue in the standard NFS driver on OpenStack, that uses
>> qemu-img and libvirt to create snapshots of volumes. It uses qemu-img in
>> the Controller to manage the snapshots when the volume is not attached
>> (offline) or calls the Compute (which calls libvirt) to manage snapshots if
>> the volume is attached (online). When I try to create/delete snapshots from
>> a snapshot chain. There are 3 situations:
>>
>> 1 - I create/delete the snapshots in Cinder (it uses qemu-img). It goes
>> OK! I can delete and I can create snapshots.
>> 2 - I create/delete the snapshots, in online mode (it uses libvirt). It
>> goes Ok, as weel.
>> 3 - I create the snapshots in Cinder (offline) and delete then in online
>> mode (using libvirt), then it fails with this message[1]:
>>
>> libvirtError: invalid argument: could not find image
>> 'volume-13cb83a2-880f-40e8-b60e-7e805eed76f9.d024731c-bdc3-4943-91c0-215a93ee2cf4'
>> in chain for '/opt/stack/data/nova/mnt/a3b4c6ddd9bf82edd4f726872be58d
>> 05/volume-13cb83a2-880f-40e8-b60e-7e805eed76f9'
>>
>> But, in this folder, there the backing files are there[2] and they are
>> chained as think it suppose to be[3].
>>
>> The version for the 2 hosts in tests are:
>> Controller/Cinder node: qemu-img version 2.0.0 && libvirt 1.2.2-0ubuntu13
>> Compute node: qemu-img version 2.5.0 && libvirt-1.3.1-1ubuntu10
>>
>> Is there any compatibility problem between libvirt and qemu-img
>> snapshots? Have you guys found any problem like that?
>>
>> Erlon
>> ----------------------------------
>>
>>
>> [1] http://paste.openstack.org/show/543270/
>> [2] http://paste.openstack.org/show/543273/
>> [3] http://paste.openstack.org/show/543274/
>>
>
>
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