[Pacemaker] drbd on heartbeat links

[Dan Frincu]

Dan Frincu wrote:
> Hi,
>
> 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, 
Correction
> the resource-only fencing does that for you, 
The resource-only fencing restricts a drbd resource from running on that 
node (puts it in unconfigured state, no primary/secondary, no 
replication), it doesn't fence the node, don't want to be misunderstood.
> the only thing you need to do is to add the drbd fence handlers in 
> /etc/drbd.conf.
>        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?
>
> Regards,
>
> Dan
>
>> 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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>>
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>> Bugs: 
>> http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker 
>>
>>   
>

-- 
Dan FRINCU
Systems Engineer
CCNA, RHCE
Streamwide Romania