[Linux-cluster] 2-node cluster fence loop

[Digimer]

Have you tried simple things like disabling iptables or selinux, just to 
test? If that doesn't work, and it's a small cluster, try unicast and 
see if that helps (again, even if just to test).

On 12/06/14 10:29 AM, Arun G Nair wrote:
> 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 at alteeve.ca
> <mailto:lists at alteeve.ca>> wrote:
>
>     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,
>
>
>     Hi,
>
>        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
>
>     --
>     Digimer
>     Papers and Projects: https://alteeve.ca/w/
>     What if the cure for cancer is trapped in the mind of a person
>     without access to education?
>
>     --
>     Linux-cluster mailing list
>     Linux-cluster at redhat.com <mailto:Linux-cluster at redhat.com>
>     https://www.redhat.com/__mailman/listinfo/linux-cluster
>     <https://www.redhat.com/mailman/listinfo/linux-cluster>
>
>
>
>
> --
> Arun G Nair
> Sr. Sysadmin
> Dimension Data | Ph: (800) 664-9973
> Feedback? We're listening <http://www.surveymonkey.com/s/XRCYXBH>
>
>


-- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without 
access to education?