[openstack-dev] [Nova][Cinder] Cleanly detaching volumes from failed nodes

Avishay Traeger avishay at stratoscale.com
Sun Feb 7 06:38:20 UTC 2016

On Thu, Feb 4, 2016 at 6:38 PM, Walter A. Boring IV <walter.boring at hpe.com>

> My plan was to store the connector object at attach_volume time.   I was
> going to add an additional column to the cinder volume attachment table
> that stores the connector that came from nova.   The problem is live
> migration.   After live migration the connector is out of date.  Cinder
> doesn't have an existing API to update attachment.  That will have to be
> added, so that the connector info can be updated.
> We have needed this for force detach for some time now.
> It's on my list, but most likely not until N, or at least not until the
> microversions land in Cinder.
> Walt

I think live migration should probably just be a second attachment - during
the migration you have two attachments, then you detach the first.  I think
this is correct because as far as Cinder and the storage is concerned,
there are two attachments.  I think most of this mess started because we
were trying to make the volume status reflect the status in Cinder and
Nova.  If the status reflects only Cinder's (and the storage backends')
status, things because simpler.  (Might need to pass an extra flag on the
second attach to over-ride any "no multiattach" policies that exist.)

*Avishay Traeger, PhD*
*System Architect*

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E-mail: avishay at stratoscale.com

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