[Linux-cluster] Repeated fencing

[Carlos Maiolino]

On Tue, Feb 23, 2010 at 11:13:33AM -0600, Doug Tucker wrote:
> > Hi Doug, maybe you can avoid this kind of problem using a quorumdisk partition. a two node cluster is split-brain prone and with a quorumdisk partition you can avoid split-brain situations, which probably is causing this behavior.
> > 
> > So, about use a cross-over (or straight) cable, I don't know any issue about it, but, try to check if it's using full-duplex mode. half-duplex mode on cross-over linked machines probably will cause heartbeat problems.
> > 
> > cya..
> 
> Can you give me a little info about "split-brain" issues?  I don't
> understand what you mean by that, and what I'm solving with a
> quorumdisk.  And it has always worked fine, it just started happening
> after the install of this newer kernel/gfs module.  The other 2 node
> cluster is still rock solid.  Also, the network interfaces on the
> crossover are full duplex.  Thanks for writing back, you're the first
> person who offered anything.
> 
> 
> 
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Hi Doug,

a split-brain is a situation when (in this case) the cluster communication channel are interrupted (dua any situation), and each node thinks that "it is the remaining node, and the another node is offline. So, with quroumdisk, you'll have a second "heartbeat" system, where both nodes will have a common partition and write metadata information to it. In case a heartbeat fail (cross-over cable in your environment), the cluster will still check if the quorumdisk is still available, and take decisions based on qdisk configuration.

Sorry for this poor explainin, I really needed to write it as fast as I can, so, you can check these documents for help and a well understanding about qdisk

http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/Cluster_Administration/s1-qdisk-considerations-CA.html
http://www.linuxdynasty.org/howto-setup-a-quorum-disk.html

any doubts ask us..



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Best Regards

Carlos Eduardo Maiolino
Support engineer
Red Hat - Global Support Services