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On 04/03/2014 09:34 AM, Murray, Paul (HP Cloud Services) wrote:
> Hi Sylvain,
>
> I would go with keeping AZs exclusive. It is a well-established concept
> even if it is up to providers to implement what it actually means in
> terms of isolation. Some good use cases have been presented on this
> topic recently, but for me they suggest we should develop a better
> concept rather than bend the meaning of the old one. We certainly don’t
> have hosts in more than one AZ in HP Cloud and I think some of our users
> would be very surprised if we changed that.

I'm okay with only allowing hosts to be within a single availability 
zone, but in that case maybe we could have a per-instance way of 
matching host aggregate metadata when booting the instance--maybe a 
special form of scheduler hints?  This would be analogous to the 
existing matching of flavor metadata.

Also, while we're looking at availability zones I'd like to point out a 
bug I reported last year (https://bugs.launchpad.net/nova/+bug/1213224) 
where you can specify multiple aggregates with the same zone name. 
Since the user can only specify the zone name, this makes it 
indeterminate which aggregate is actually used.

Chris