[ClusterLabs] can't start/stop a drbd resource with pacemaker
kgaillot at redhat.com
Mon Jul 18 13:29:01 EDT 2016
On 07/18/2016 11:56 AM, Lentes, Bernd wrote:
> ----- On Jul 18, 2016, at 4:04 PM, Ken Gaillot kgaillot at redhat.com wrote:
>>> Is there a way to manipulate the scores ? Is the score -INFINITY because the
>>> resource is stopped
>>> or is the resource stopped because the score is -INFINITY ?
>> Yes, yes and yes ;-)
>> You can manipulate the scores in the configuration. The different
>> high-level tools (crm, pcs, etc.) have their own syntax for specifying
>> scores, but each constraint has a score, and resource stickiness is a
>> score. The cluster sums up all the scores that apply to a given resource
>> per node, and places the resource on the node with the highest score.
>> From the cluster's point of view, the resource is stopped because the
>> score is negative on all nodes.
>> However, the crm command's syntax uses "stop" and "start" indirectly.
>> "crm stop" (and "pcs resource disable") simply adds constraints with
>> negative scores to all nodes, to make the cluster stop the resource.
>> "crm start" (and "pcs resource enable") simply removes those
>> constraints. So, from the point of view of using crm, "stopping" the
>> resource creates the negative scores, which then makes the cluster
>> actually stop the resource.
> Hi Ken,
> thanks for your help.
> Can i edit them directly ? Or do i have to make a circuit with constraints ?
Constraints are how they are edited.
Stop/start aren't used in normal operation, typically only when you're
doing some sort of maintenance. Normally, you just leave everything
"started", and the cluster starts/stops services as needed.
Constraints let you set scores for conditions you desire, such as
preferring a more powerful node, keeping two resources together, etc.
> Is pcs available for Suse SLES 11 SP4 ?
> I searched for it but didn't find it.
> Is it a good idea to use pcs because i read crm is deprecated ?
No, crm is still actively maintained and fully supported on SuSE. Pcs is
used on Fedora/RHEL/CentOS. The two are largely equivalent in
functionality; only the syntax is different.
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