On Wed, May 30, 2007 at 10:12:41AM -0400, Neil Watson wrote: > On Wed, May 30, 2007 at 09:08:19AM -0500, David Teigland wrote: > >>> During a disaster recovery test three nodes of a three node cluster > >>> were caused to fail. A single node was rebooted to attempt a > >>> recovery. The node failed to bring back the service and reports these > >>> errors: > > > >Sorry, I failed to read that properly. In a three node cluster you need > >two nodes for quorum, so you need to bring two back before anything will > >happen. > > So this plan will fail :(. We would need to have four nodes: two at > the main data centre and two at the DR centre? That is unexpected. > There is no way around this? Quorum is a voting scheme. Each node has one vote by default and the cluster needs a majority of all possible votes to do anything. So, with a four node cluster (each node with one vote) your cluster would require three three of them for quorum (3 of 4 votes for a majority). Two node clusters are a special case where we can override the normal quorum rule and allow just one of the nodes to run on its own. Qdisk (a quorum disk) is a system you can set up to assign votes to a shared disk. A cluster that can access the disk gets the votes from the disk. That's the standard way to work around quorum restrictions. Dave -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
