[openstack-dev] [nova][scheduler] Availability Zones and Host aggregates..

Chris Friesen chris.friesen at windriver.com
Thu Mar 27 18:52:24 UTC 2014

On 03/27/2014 12:28 PM, Day, Phil wrote:

> Personally I'm a bit worried about users having too fine a
> granularity over where they place a sever - AZs are generally few and
> big so you can afford to allow this and not have capacity issues, but
> if I had to expose 40 different rack based zones it would be pretty
> hard to stop everyone pilling into the first or last - when really
> want they want to say is "not the same as"   or "the same as"  -
> which makes me wonder if this is really the right way to go.    It
> feels more like what we really want is some form of affinity and
> anti-affinity rules  rather than an explicit choice of a particular
> group.

I suspect in many cases server groups with affinity rules would go a 
long way, but currently the server group policies only select based on 
compute node.

It'd be nice to be able to do a heat template where you could specify 
things like "put these three servers on separate hosts from each other, 
and these other two servers on separate hosts from each other (but maybe 
on the same hosts as the first set of servers), and they all have to be 
on the same network segment because they talk to each other a lot and I 
want to minimize latency, and they all need access to the same shared 
instance storage for live migration".


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