[Linux-cluster] 2-node cluster fence loop

T, Muthukumar muthukumar.t at hp.com
Wed Jun 11 18:11:51 UTC 2014

Hi all,

When your cluster nodes got panic while starting cman services that can’t called as fence loop that is called as misconfiguration of POST JOIN DELAY setting.

By default post_join_delay setting is 3 seconds, while starting cman on a cluster node it will try to get the status of other cluster nodes to make sure the integrity of the cluster services if other nodes are not responsive till post_join_delay timeout, other cluster node fenced by this node to ensure integrity (there may be chance that node already formed the cluster and started cluster services)

Fence looping is different one, this is happen when there is a failure in heart beat switch for long time.

Thanks & Regards

Muthukumar T
Production Engineering - UNIX

From: linux-cluster-bounces at redhat.com [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Arun G Nair
Sent: Wednesday, June 11, 2014 8:19 PM
To: linux-cluster at redhat.com
Subject: [Linux-cluster] 2-node cluster fence loop


   What are the reasons for fence loops when only cman is started ? We have an RHEL 6.5 2-node cluster which goes in to a fence loop and every time we start cman on both nodes. Either one fences the other. Multicast seems to be working properly. My understanding is that without rgmanager running there won't be a multicast group subscription ? I don't see the multicast address in 'netstat -g' unless rgmanager is running. I've tried to increase the fence post_join_delay but one of the nodes still gets fenced.
The cluster works fine if we use unicast UDP.

Arun G Nair
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