[ClusterLabs] question about equal resource distribution

[Ilia Sokolinski]

Thank you!

What quantity does pacemaker tries to equalize - number of running resources per node or total stickiness per node?

Suppose I have a bunch of web server groups each with IPaddr and apache resources, and a fewer number of database groups each with IPaddr, postgres and LVM resources.

In that case, does it mean that 3 web server groups are weighted the same as 2 database groups in terms of distribution?

Ilia



> On Feb 17, 2017, at 2:58 AM, Kristoffer Grönlund <deceiver.g at gmail.com> wrote:
> 
> Ilia Sokolinski <ilia at clearskydata.com> writes:
> 
>> Suppose I have a N node cluster where N > 2 running m*N resources. Resources don’t have preferred nodes, but since resources take RAM and CPU it is important to distribute them equally among the nodes.
>> Will pacemaker do the equal distribution, e.g. m resources per node?
>> If a node fails, will pacemaker redistribute the resources equally too, e.g. m * N/(N-1) per node?
>> 
>> I don’t see any settings controlling this behavior in the documentation, but perhaps, pacemaker tries to be “fair” by default.
>> 
> 
> Yes, pacemaker tries to allocate resources evenly by default, and will
> move resources when nodes fail in order to maintain that.
> 
> There are several different mechanisms that influence this behaviour:
> 
> * Any placement constraints in general influence where resources are
>  allocated.
> 
> * You can set resource-stickiness to a non-zero value which determines
>  to which degree Pacemaker prefers to leave resources running where
>  they are. The score is in relation to other placement scores, like
>  constraint scores etc. This can be set for individual resources or
>  globally. [1]
> 
> * If you have an asymmetrical cluster, resources have to be manually
>  allocated to nodes via constraints, see [2]
> 
> [1]: http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Explained/index.html#s-resource-options
> [2]: http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Explained/index.html#_asymmetrical_opt_in_clusters
> 
> Cheers,
> Kristoffer
> 
>> Thanks 
>> 
>> Ilia Sokolinski
>> _______________________________________________
>> Users mailing list: Users at clusterlabs.org
>> http://lists.clusterlabs.org/mailman/listinfo/users
>> 
>> Project Home: http://www.clusterlabs.org
>> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
>> Bugs: http://bugs.clusterlabs.org
> 
> -- 
> // Kristoffer Grönlund
> // kgronlund at suse.com