[openstack-dev] [Nova] why don't we deal with "claims" when live migrating an instance?

yunhong jiang yunhong.jiang at linux.intel.com
Fri Jan 17 22:40:59 UTC 2014

On Fri, 2014-01-17 at 09:39 -0800, Vishvananda Ishaya wrote:
> On Jan 16, 2014, at 9:41 PM, Jiang, Yunhong <yunhong.jiang at intel.com>
> wrote:
> > I noticed the BP has been approved, but I really want to understand
> > more on the reason, can anyone provide me some hints?
> >  
> > In the BP, it states that “For resize, we need to confirm, as we
> > want to give end user an opportunity to rollback”. But why do we
> > want to give user an opportunity to rollback to resize? And why that
> > reason does not apply to cold migration and live migration?
> The confirm is so the user can verify that the instance is still
> functional in the new state. We leave the old instance around so they
> can abort and return to the old instance if something goes wrong. This
> could apply to cold migration as well since it uses the same code
> paths, but it definitely does not make sense in the case of
> live-migration, because there is no old vm to revert to.

Thanks for clarification.
> In the case of cold migration, the state is quite confusing as
> “RESIZE_VERIFY”, and the need to confirm is not immediately obvious so
> I think that is driving the change.
I didn't saw patch to change the state in that BP, so possibly it's
still on way.

So basically the idea is, while we keep the implementation code path
combined for resize/code migration as much as possible, but we will keep
them different from user point of view, like different configuration
option, different state etc, right?

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