[Pacemaker] Contraining clones per node

[Michael Schwartzkopff]

Am Montag, 30. November 2009 14:07:23 schrieb Jens.Braeuer at rohde-schwarz.com:
> Hi everyone,
>
> i have been into heartbeat 2 and pacemaker for some time now and wonder
> wheather i can use it in more than just the "normal" HA situation. However
> going through the excelent "Pacemaker Configuration Explained" or the
> Linux HA Cluster book by Michael Schwarzkopff, i still have no idea how to
> configure pacemaker for my scenario.

Thanks ;-)

> My environment consists of multiple servers (~40), each with one or more
> cpu-cores. I have two application-types called A and B (services like eg.
> apache), that each use one cpu core. A is mission critical, B is optional.
> So what i want to express is that there should be 20 A's and the remaining
> cpu's may be used by B's. When a node executing A's fails, it is perfectly
> ok to shut down B's to make cpu cores available for A's to be started.
>
> Any idea how to do this?

In pacemaker resources have a meta_attribute "priority". If there are not 
enough nodes available ton run all resources the resources with higher 
priority are run.

so make a clone of to start 20  times A. Resource A has a priority of 20. Make 
a clone of B with B having a priority of 10.

> Going through the various examples in the book and pdf, i found examples
> on how to use instance-attributes for one resource. That mean things like
> "start apache only on host with more than XY ram or MN cpu speed".
> However, in my scenario i thing i need contraints that invole the number
> of resources on the host. An example would be "the sum of A's and B's
> started on node must be less or equal the number of cpu cores". But even
> going through the parameters supplied to ocf-agent (page 72 in the
> pacemaker explained pdf), it seem i am unable to figure out how many
> clones a currently runs.

Resource allocation is a feature of the next verison. As far as I know it does 
not work up to now. At least it is not well tested.

> Is pacemaker able to handle such constraints? Is there some work-around
> (eg with score-values) to emulate such behavior?

See prio above.

> any ideas/hints/comments are very welcome.
> best regards,
>
> Jens Bräuer

Greetings to Munich.

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Dr. Michael Schwartzkopff
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