[Pacemaker] drbd on heartbeat links

Dan Frincu dfrincu at streamwide.ro
Tue Nov 2 11:15:39 EDT 2010


Pavlos Parissis wrote:
> Hi,
> I am trying to figure out how I can resolve the following scenario
> Facts
> 3 nodes
> 2 DRBD ms resource
> 2 group resource
> by default drbd1/group1 runs on node-01 and drbd2/group2 runs on node2
> drbd1/group1  can only run on node-01 and node-03
> drbd2/group2  can only run on node-02 and node-03
> DRBD fencing_policy is resource-only [1]
> 2 heartbeat links and one of them used by DRBD communication
> Scenario
> 1) node-01 loses both heartbeat links
> 2) DRBD monitor detects first the absence of the drbd communication
> and does resource fencing by add location constraint which prevent
> drbd1 to run on node3
> 3) pacemaker fencing kicks in and kills node-01
> due to location constraint created at step 2, drbd1/group1 can run in
> the cluster
I don't understand exactly what you mean by this. Resource-only fencing 
would create a -inf score on node1 when the node loses the drbd 
communication channel (the only one drbd uses), however you could still 
have heartbeat communication available via the secondary link, then you 
shouldn't fence the entire node, the resource-only fencing does that for 
you, the only thing you need to do is to add the drbd fence handlers in 
        handlers {
                fence-peer "/usr/lib/drbd/crm-fence-peer.sh";
                after-resync-target "/usr/lib/drbd/crm-unfence-peer.sh";

Is this what you meant?



> Any ideas?
> Cheers,
> Pavlos
> [1] it is not resource-and-stonith because in the scenario where a
> node has the role of primary for drbd1 and secondary for drbd2, could
> be fenced because the primary node of drbd2 have in fencing_policy
> resource-and-stonith
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Systems Engineer
Streamwide Romania

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