-----Original message----- To: The Pacemaker cluster resource manager <pacemaker@oss.clusterlabs.org>; From: Christoph Herrmann <c.herrm...@science-computing.de> Sent: Tue 11-01-2011 10:24 Subject: Re: [Pacemaker] Split-site cluster in two locations > As long as you have only two computing centers it doesn't matter if you run a > corosync > only piece or whatever on a physikal or a virtual machine. The question is: > How to > configure a four node (or six node, an even number bigger then two) > corosync/pacemaker > cluster to continue services if you have a blackout in one computing center > (you will > always loose (at least) one half of your nodes), but to shutdown everything > if > you have > less then half of the node available. Are there any best practices on how to > deal with > clusters in two computing centers? Anything like an external quorum node or a > quorum > partition? I'd like to set the expected-quorum-votes to "3" but this is not > possible > (with corosync-1.2.6 and pacemaker-1.1.2 on SLES11 SP1) Does anybody know why? > Currently, the only way I can figure out is to run the cluster with > no-quorum-policy="ignore". But I don't like that. Any suggestions?
Apart from the number of nodes in de datacenter: with 2 datacentre's you have another issue: How do you know which DC is reachable (from you're clients point of view) when the communication between DC fails? Best fix for this would be a node at a third DC but you still run into problems with the fencing devices. I doubt you can remotely power-off the non-responding DC :-) So a split brain situation is likely to happen sometime. So for 100% data integrity I think it is best to let the cluster freeze itself... Best Regards, Robert van Leeuwen _______________________________________________ Pacemaker mailing list: Pacemaker@oss.clusterlabs.org 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://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker
