[openstack-dev] Next steps for Whole Host allocation / Pclouds

Mike Spreitzer mspreitz at us.ibm.com
Wed Jan 22 14:53:31 UTC 2014

Jay Pipes <jaypipes at gmail.com> wrote on 01/21/2014 08:50:36 PM:
> On Tue, 2014-01-21 at 14:28 +0000, Day, Phil wrote:
> > > >
> > > > I think there is clear water between this and the existing 
> aggregate based
> > > isolation.  I also think this is a different use case from 
> reservations.   It's
> > > *mostly* like a new scheduler hint, but because it has billing 
> impacts I think it
> > > needs to be more than just that - for example the ability to request 
> > > dedicated instance is something that should be controlled by a 
> specific role.

Please help me see this clear water.  At the icehouse summit I heard the 
concern that without reservations there will be an unacceptably high 
probability that a nova-boot request will be unsatisfiable due to lack of 
hosts that are fully idle.  Why is that not a concern now?

> > > IMHO, this model is interesting but hard to use for operators, 
> because they
> > > don't have visibility on the capacity.  ...

In what sense do operators not have visibility on the capacity?

> ...
> Yup, agreed. It's difficult to guess what the capacity implications
> would be without having solid numbers on customer demands for this
> functionality, including hard data on how long such instances would
> typically live (see my previous point about re-using compute hosts for
> other purposes once the last dedicated instance is terminated on that
> host).

That is what I find hardest about designing stuff for general purpose use 
--- we get to assume little about the usage.

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