[Pacemaker] placement-strategy=minimal - placing and logging

Vladimir ml at foomx.de
Fri Mar 8 11:43:54 EST 2013

On Fri, 8 Mar 2013 12:08:05 +0100
Lars Marowsky-Bree <lmb at suse.com> wrote:

> On 2013-03-08T11:59:33, Vladimir <ml at foomx.de> wrote:
> > Collocations were exactly what I try to avoid. The setup is planned
> > to get >15 resources (and an upper limit is not defined). I think
> > it would get pretty hard to consider all possible collocations,
> > especially if a kind of automated deployment is regarded. Using
> > larger sets of collocation makes the configuration more difficult
> > to read an especially to maintain.
> I see your point. But the collocations don't really get more difficult
> with the number of resources, but mostly node size.

I think node size means the number of nodes. Sorry, I didn't describe it
properly. The >15 resources I mentioned are distributed over at least 3
nodes >(probably more + 1 failover node). The problem I see is that my
setup uses Resource Groups because in my opinion the config stays much
cleaner than colocating multiple resources. The setup looks something

Resource Group: group-01
Resource Group: group-02
Resource Group: group-03

Maybe Collocation Sets could decrease the count of config entries.
Especially to get an overview about the resources I think crm_mon
output is much clearer when using Resource Groups. I haven't found an
efficient way to show the relations between colocations beside wrapper
scripts which parse "crm configure show" output.

I already had to work around utilization by defining utilization for
the first resource in the Resource Group. Defining utilization for
Resource Groups didn't work for me. Furthermore I can remember that
there were also problems by colocating Resource Groups. I would like to
stay by the given resource layout.

What are your experience? Is it possible to combine Resource Groups and
colocations? Or do I have to give up Resource Groups when using
colocations? If so I maybe have to restructure my resource setup to
colocations only.

> > Ok, I see but I'm looking for a possibility to monitor such states
> > to be informed if a resource can't be started because of lack of
> > provided utilization. 
> > 
> > Does anybody has an idea about that issue? 
> Running the PE is the only choice right now. I think with crm_mon
> you'll also be informed about stopped resources; basically you'd want
> to be told about everything not explicitly stopped (e.g.,
> target-role != stopped), right?

That could be an approach. Sorry if a beginner question but I know
policy engine only in form of ptest command. Did you think to parse the
output of ptest and crm_mon? Or do you see a more straight forward way
to monitor the cluster state?

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