We have multicast enabled on the switch. I've also tried the multicast.py tool from RH's knowledge base to test multicast and I see the expected output, though the tool uses a different multicast IP( guess that shouldn't matter). I've tried increasing the post_join_delay to 360 seconds to give me enough time to check everything on both the nodes. One node still gets fenced. `clustat` output says the other node is offline on both servers. So one node can't see the other one ? This again points to issue with multicast. Any other clues as to what/where to look ?
On Wed, Jun 11, 2014 at 8:33 PM, Digimer <lists@xxxxxxxxxx> wrote:
Hi,On 11/06/14 10:48 AM, Arun G Nair wrote:
Hello,
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.
Thanks,
When cman starts, it waits post_join_delay seconds for the peer to connect. If, after that time expires (6 seconds by default, iirc), it gives up and calls a fence against the peer to put it into a known state.
Corosync is what determines membership, and it is started by cman. The rgmanager only handles resource start/stop/relocate/recovery and has nothing to do with fencing directly. Corosync is what uses multicast.
So as you seem to have already surmised, multicast is probably not working in your environment. Have you enabled multicast traffic on the firewall? Do your switches support multicast properly?
digimer
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