[Pacemaker] Configuring 3rd Node as Quorum Node in 2 Node Cluster

Andreas Kurz andreas at hastexo.com
Fri Feb 24 08:26:59 EST 2012 

Hello,

On 02/23/2012 03:59 PM, Andrew Martin wrote:
> I set up the 3rd node ("quorum") yesterday by only installing heartbeat,
> not pacemaker. Is pacemaker necessary as well? I commented out the
> following lines in its ha.cf since it is always going to be running in
> standby:
> autojoin none
> mcast eth0 239.0.0.43 694 1 0
> bcast eth0
> warntime 5
> deadtime 15
> initdead 60
> keepalive 2
> node node1
> node node2
> node quorum
> #crm respawn
> #respawn hacluster /usr/lib/heartbeat/dopd
> #apiauth dopd gid=haclient uid=hacluster
>

Hmm ... IIRC I had to enable ccm in ha.cf on the third node during my
last heartbeat tests to enable a quorum node:

respawn hacluster       ccm

> Since this quorum node only has a single ethernet interface, can it be
> used for both the mcast and bcast parameters? How are both the multicast
> and broadcast pathways used for node communication? After saving these
> parameters and reloading heartbeat on all nodes, the "quorum" node is
> listed as offline in the cluster. Is there something missing in my
> configuration that is preventing it from communicating with the rest of
> the cluster?

cl_status and hbclient should give you some membership information, and
there should be some log entries on the nodes running Pacemaker. I don't
think the node will show up as ONLINE in crm_mon if no Pacemaker is
running there.

You only need the communication settings you also used for node1/2 on
the shared network ... so only the mcast directive is needed/possible on
node3.

> 
> Also, another more general question about the failover - node1 and node2
> are each connected to the shared network over br0 and connected directly
> to each other with a crossover cable over br1:
>       --------------------      ----------
>       |   Shared Network |------| quorum |
>       --------------------      ----------
>                |
>         br0  /   \  br0
>            /       \
>  ---------           ---------
>  | node1 | --------- | node2 | 
>  ---------     br1   ---------
> 
> The corresponding configuration in ha.cf is
> autojoin none
> mcast br0 239.0.0.43 694 1 0
> bcast br1
> warntime 5
> ....
> 
> If br0 to one of the nodes were to be cut when the "quorum" node was
> down, would they still be able to communicate over br1 (e.g. to maintain
> quorum between themselves and fail over to the other node that still has
> an active br0)? 

as long as node1/2 can communicate the cluster has quorum, to fail over
resources to the node with best connectivity: configure ping resource
agent and constraints, there is a chapter in "Pacemake Explained" on
clusterlabs.org ... http://goo.gl/x7dwK

Regards,
Andreas

-- 
Need help with Pacemaker?
http://www.hastexo.com/now

> 
> Thanks,
> 
> Andrew
> 
> ------------------------------------------------------------------------
> *From: *"Andreas Kurz" <andreas at hastexo.com>
> *To: *pacemaker at oss.clusterlabs.org
> *Sent: *Monday, January 23, 2012 1:53:27 PM
> *Subject: *Re: [Pacemaker] Configuring 3rd Node as Quorum Node in
> 2        Node        Cluster
> 
> On 01/23/2012 03:36 PM, Andrew Martin wrote:
>> I think I will configure the 3rd (quorum) node in standby mode. In the
>> near future I am looking into setting up 2 additional clusters (each of
>> these are also 2-node clusters) and would like to use this same server
>> as the quorum node for those clusters as well. Is this possible? If so,
>> how do I have to configure heartbeat (or multiple instances of
>> heartbeat) to join multiple clusters at once and act as the quorum node
>> in each?
> 
> No, multiple heartbeat instances per node are not supported ... but why
> not creating minimal VM instances ... though not to minimal, as you have
> a good chance that theses standby instances become DC role.
> 
> Regards,
> Andreas
> 
> -- 
> Need help with Pacemaker?
> http://www.hastexo.com/now
> 
>>
>> Thanks,
>>
>> Andrew
>>
>> ------------------------------------------------------------------------
>> *From: *"Andreas Kurz" <andreas at hastexo.com>
>> *To: *pacemaker at oss.clusterlabs.org
>> *Sent: *Friday, January 13, 2012 6:35:48 AM
>> *Subject: *Re: [Pacemaker] Configuring 3rd Node as Quorum Node in 2
>> Node        Cluster
>>
>> On 01/13/2012 12:32 PM, Ivan Savčić | Epix wrote:
>>> On 1/11/2012 8:28 AM, Florian Haas wrote:
>>>> Another option would be to permanently run the 3rd node in standby mode.
>>>
>>> Just wondering, wouldn't the standby mode prevent that node from
>>> performing the fencing actions? Also, can it act as DC then?
>>
>> It would run no resources (including stonith resources) but can be the DC.
>>
>> Another option for running a "pure" quorum node would be to only start
>> CCM but not pacemaker ... though that setup looks quite strange e.g. in
>> crm_mon output ....
>>
>> Regards,
>> Andreas
>>
>> --
>> Need help with Pacemaker?
>> http://www.hastexo.com/now
>>
>>>
>>> Thanks,
>>> Ivan
>>>
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>>
>>
>>
>>
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>>
>>
>>
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>> Bugs: http://bugs.clusterlabs.org
> 
> 
> 
> _______________________________________________
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> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
> 
> Project Home: http://www.clusterlabs.org
> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
> Bugs: http://bugs.clusterlabs.org
> 
> 
> 
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> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
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> Bugs: http://bugs.clusterlabs.org


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