[Pacemaker] Resource capacity limit

[Andrew Beekhof]

On Thu, Nov 5, 2009 at 8:50 PM, Michael Schwartzkopff <misch at multinet.de> wrote:
> Hi,
>
> on the list was a discussion about resource capacity limits. Yan Gao also
> implemented it.
>
> As far as I understood the discussion the solution is to attach nodes and
> resources capacity limits. Resources are distributed on the nodes of a cluster
> according to its capacatiy needs. They would be migrated or shutdown if the
> capacity limits on the node are not met.
>
> My question is: Can the capacity figures of the resources be made dynamically?

You can, but you probably don't want to.
For example, free RAM and CPU load are two things that absolutely make
no sense to include in such calculations.

Consider how it works:

- The node starts and reports 2Gb of RAM
- We place a service there that reserves 512Mb
- The cluster knows there is 1.5Gb remaining
- We place two more services there that also reserve 512Mb each

If the amount of RAM at the beginning was the amount free, then when
you updated it to be 512Mb the PE would run and stop two of the
resources!

You always want to feed the cluster the total amount of RAM installed
which, at most, you'd query when the cluster starts on that node.
>
> So i.e. for every monitor operation the CRM updates the capacity usage figures
> of the resource. So the cluster could react dynamically oin the actual
> capacity of a resource.
>
> Greetings,
>
> Michael.
>
> _______________________________________________
> Pacemaker mailing list
> Pacemaker at oss.clusterlabs.org
> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>