Open Stack

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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