openstack team mailing list archive

[Vishvananda Ishaya <vishvananda@xxxxxxxxx>]

On Mar 20, 2013, at 11:20 AM, Brano Zarnovican <zarnovican@xxxxxxxxx> wrote:

> On Wed, Mar 20, 2013 at 5:06 PM, Vishvananda Ishaya
> <vishvananda@xxxxxxxxx> wrote:
>>> 2) Wipeout connection_info after disconnect. At least for Netapp
>>> provider it makes no sense to retain the info which is no longer valid
>>> anyway.
>> 
>> This seems reasonable. In fact, the whole block_device_mapping item
>> can be deleted after disconnect.
> 
> You cannot delete the whole bdm entry when you stop an instance. Volume
> is disconnected but you still need that info for next start-instance to reattach
> the volume.
> 
> You could nullify 'connection_info' value in bdm.. but I have never
> seen bdm with
> connection_info blank. No idea how many things that would break..
> 
>> I need a little more context to
>> understand if this will actually help the issue that you are seeing
> 
> If there is no information in bdm that this volume *had* LUN id 5, then there
> is no way somebody will send it down to disconnect_volume. And no way
> for me to delete a wrong device which happens to be using LUN id 5 now.
> 
>> though. The double disconnects are usually very close together, so
>> there shouldn't be a new lun assigned in between two of them anyway.
>> Have you identified a case where a second disconnect is called much
>> later?
> 
> Yes.
> The first disconnect is when you stop an instance with attached volume.
> The second one is when you terminate that stopped instance.
> https://github.com/openstack/nova/blob/stable/essex/nova/virt/libvirt/connection.py#L470
> 
> In-between those two disconnects, the volume is in state
> 'available/detached' and there
> is a (non-deleted) bdm entry with connection_info regarding the last attachment.

Thanks for the explanation. In the current code stop does not detach the volume
and I don't think it should. So it looks like this only affects essex. In fact
the proper fix for essex may just be to do the same: don't detach volumes on stop.

In general actually detaching the volume should be also removing the
bdm.

Vish