[openstack-dev] [OpenStack][Nova][cold migration] Why we need confirm resize after cold migration

Russell Bryant rbryant at redhat.com
Wed Jan 8 14:49:05 UTC 2014

On 01/08/2014 04:52 AM, Jay Lau wrote:
> Greetings,
> I have a question related to cold migration.
> Now in OpenStack nova, we support live migration, cold migration and resize.
> For live migration, we do not need to confirm after live migration finished.
> For resize, we need to confirm, as we want to give end user an
> opportunity to rollback.
> The problem is cold migration, because cold migration and resize share
> same code path, so once I submit a cold migration request and after the
> cold migration finished, the VM will goes to verify_resize state, and I
> need to confirm resize. I felt a bit confused by this, why do I need to
> verify resize for a cold migration operation? Why not reset the VM to
> original state directly after cold migration?

The confirm step definitely makes more sense for the resize case.  I'm
not sure if there was a strong reason why it was also needed for cold

If nobody comes up with a good reason to keep it, I'm fine with removing
it.  It can't be changed in the v2 API, though.  This would be a v3 only

> Also, I think that probably we need split compute.api.resize() to two
> apis: one is for resize and the other is for cold migrations.
> 1) The VM state can be either ACTIVE and STOPPED for a resize operation
> 2) The VM state must be STOPPED for a cold migrate operation.

I'm not sure why would require different states here, though.  ACTIVE
and STOPPED are allowed now.

Russell Bryant

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