[ClusterLabs] Setting n+1 cluster steps

[Ken Gaillot]

----- Original Message -----
> Hi  ,
> 
> I am referring to cluster from scratch document by pacemaker which only talks
> about configuration to 1+1 cluster .
> I need to set n+1 and n+m clusters .Can someone please send me the
> information where it describes the steps to set these configurations .

Every cluster is unique, so Clusters From Scratch just gives you an example
to show the basic workings. You're probably using a high-level configuration
tool such as crm or pcs; refer to its documentation for how to add nodes.

Usually it's as simple as

   pcs cluster node add $NODENAME --start

to add a node to an existing cluster. Every situation is different however,
so you'll have to research and experiment. If you configured two_node in
corosync.conf, or no-quorum-policy=ignore in Pacemaker, you'll want to
remove that when going above 2 nodes.

For N+1/N+M you just add all your nodes to the cluster, and Pacemaker
will host your resources on whichever nodes are available, automatically
moving them if one goes down or comes up. There's no need to specify
one or more nodes as "backup", but if you really want to (perhaps because
one node is slower than the rest), you can use location constraints
to prefer any node more or less than the others.

Again, refer to your configuration tool's documentation for how to
configure constraints etc., but if you want a lower-level view of how
it all works, see Pacemaker Explained:

http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Explained/index.html