Hello Blair
IMO it's a matter of capacity planning and design to minimize
fragmentation. I don't know of any mechanisms to filter this and solve
(i.e. re-balance) a posteriori. Blueprints exists, though, to allow
re-scheduling and re-balancing.
Maybe I'm wrong and there are indeed some scheduler filters out of the
box...
Anyways, I recommend you to read this:
http://rhsummit.files.wordpress.com/2014/04/deterministic-capacity-planning-for-openstack-final.pdf
and open this spreadsheet:
https://github.com/noslzzp/cloud-resource-calculator , it will show you
the optimal flavor configuration for minimal fragmetation using
different variables (vcpu, RAM, disk)
Regards
On 2014-09-24 11:08 AM, Blair Bethwaite wrote:
Hi all,
I'm trying to wrap my head around whether it's possible with the
existing scheduler filters, to put a limit per host on the number of
instances per instance-type/flavor? I don't think this is possible
with the existing filters or weights, but it seems like a fairly
common requirement.
The issue I'm thinking of using this for is that of instance-to-host
fragmentation in homogenous deployments, where there is a tendency as
the zone approaches capacity to hit a utilisation ceiling - there are
rarely any "gaps" large enough for high vcpu count instances. I'm
guessing that limiting the number of smaller instances per host would
help to alleviate this.
Looks like knocking up such a filter wouldn't be too hard, just want
to check whether there is another way...?
--
Cheers,
~Blairo
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