On 01/19/2011 01:19 AM, Parvez Shaikh wrote: > Hi all, > > *Quorum - * > The questions are bit theoretical, I have gone through documentation and > man pages and have understood that, a cluster is "quorate" if a cluster > or its partition has nodes, with votes equal to or more than > "expected_votes" in "cman" section of cluster.conf file (with no > requirement mandating use of quorum disk) > > So how does cluster being quorate or non-quorate affects functioning of > a cluster or services? If cluster is non-quorate, does it indicate an > alarming situation and why? > > If a cluster is composed of resource groups which including only IP > resource and script resource monitoring my application server listening > on IP resource(no shared disk or shared resource between cluster nodes), > then is cluster being "quorate" (or non quorate) important for services > and/or cluster? With the exception of 'two_nodes="1"', "expected_votes" should be the total votes of all nodes. Quorum is achieved once 50%+1 votes coming from the available nodes in a cluster. Without quorum, the cluster will not work. I've covered some of the theory here: http://wiki.alteeve.com/index.php/Red_Hat_Cluster_Service_3_Tutorial#An_Overview_Before_We_Begin > *Fencing - * > Is fencing and cluster being quorate or non-quorate related? I tried one > experiment, wherein I removed "fencing" for cluster nodes and shutdown > one of the nodes in cluster. And I got message in /var/log/messages > indicating fencing failed for node, and service was not failed over from > that node. So is fencing mandatory even if there is no "shared" disk > between two cluster nodes? > > Also is a cluster non-quorate in a time window when a node has failed > and has not been fenced successfully? > > Yours gratefully Without fencing, your cluster is unstable. Once a fence is needed but fails, the entire cluster will block. Please check out the link above. In the same section is a detailed example of why fencing is critical. Cheers -- Digimer E-Mail: digimer@xxxxxxxxxxx AN!Whitepapers: http://alteeve.com Node Assassin: http://nodeassassin.org -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
