[Pacemaker] 3rd node just for quorum

[Anton Altaparmakov]

Hi Klaus,

On 8 Jun 2011, at 22:21, Klaus Darilion wrote:
> Hi!
> 
> Currently I have a 2 node cluster and I want to add a 3rd node to use
> quorum to avoid split brain.
> 
> The service (DRBD+DB) should only run either on node1 or node2. Node3
> can not provide the service - it should just help the other nodes to
> find out if their network is broken or the other node's network is broken.
> 
> Is my idea useful?

Yes.  That is what we do for all our Pacemake based setups.

> How do I add such a "simple" 3rd node - just by using location
> constraints for the service to be run only on node1 or node2?

Here is an example:

root at cerberus:~# crm configure show
node cerberus \
	attributes standby="off"
node minotaur \
	attributes standby="off"
node yoda \
	attributes standby="off"
primitive res_drbd ocf:linbit:drbd \
	params drbd_resource="vmstore"
primitive res_filesystem ocf:heartbeat:Filesystem \
	params fstype="xfs" device="/dev/drbd0" directory="/vmstore" options="noatime,barrier,largeio,logbufs=8,logbsize=256k,swalloc" \
	meta target-role="Started"
primitive res_ip ocf:heartbeat:IPaddr2 \
	params ip="172.28.208.50" cidr_netmask="24" broadcast="172.28.208.255"
primitive res_nfs_server lsb:nfs-kernel-server
group group_vmstore res_filesystem res_nfs_server res_ip
ms ms_drbd res_drbd \
	meta master-max="1" master-node-max="1" clone-max="2" clone-node-max="1" notify="true" globally_unique="false"
location loc_drbd_cerberus ms_drbd 0: cerberus
location loc_drbd_minotaur ms_drbd 0: minotaur
location loc_vmstore_cerberus group_vmstore 0: cerberus
location loc_vmstore_minotaur group_vmstore 0: minotaur
colocation col_vmstore inf: group_vmstore ms_drbd:Master
order order_vmstore inf: ms_drbd:promote group_vmstore:start
property $id="cib-bootstrap-options" \
	expected-quorum-votes="3" \
	stonith-enabled="false" \
	symmetric-cluster="false" \
	pe-warn-series-max="100" \
	default-action-timeout="10" \
	pe-input-series-max="100" \
	dc-version="1.0.8-042548a451fce8400660f6031f4da6f0223dd5dd" \
	pe-error-series-max="100" \
	cluster-infrastructure="openais" \
	last-lrm-refresh="1290511853" \
	default-resource-stickiness="1000"
rsc_defaults $id="rsc-options" \
	target-role="started"

Let me know if you need anything explained...

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/