Open Stack

Hey Everyone,

Something I've been looking at with Cinder's replication (sort of the next
step in the evolution if you will) is the ability to refresh/renew in-use
volumes that were part of a migration event.

We do something similar with extend-volume on the Nova side through the use
of Instance Actions I believe, and I'm wondering how folks would feel about
the same sort of thing being added upon failover/failback for replicated
Cinder volumes?

If you're not familiar, Cinder allows a volume to be replicated to multiple
physical backend devices, and in the case of a DR situation an Operator can
failover a backend device (or even a single volume).  This process results
in Cinder making some calls to the respective backend device, it doing it's
magic and updating the Cinder Volume Model with new attachment info.

This works great, except for the case of users that have a bunch of in-use
volumes on that particular backend.  We don't currently do anything to
refresh/update them, so it's a manual process of running through a
detach/attach loop.

I'm interested in looking at creating a mechanism to "refresh" all of the
existing/current attachments as part of the Cinder Failover process.

Curious if anybody has any thoughts on this, or if anyone has already done
something related to this topic?

Thanks,
John
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