[Linux-cluster] 2-node fencing question

[David Teigland]

On Mon, Jul 31, 2006 at 01:20:07PM +0000, danwest at comcast.net wrote:

> The out-of-band IPMI is basically a crossover cable to each others
> IPMI interface.
>
> A simple test of pulling the public interface one the node with an
> active resource results in each node being fenced.  My understanding is
> that in the 2-node configuration the fencing is a race to see who can
> fence each other first.  My concerns are the following:
>  
> 1)       If it is indeed a race it seems like both nodes successfully
> issue a /sbin/fence_ipmilan (ipmi_tool) resulting in both nodes being
> fenced.

Because of this race you should use a network power switch that forces the
two fencing operations to be serialized, then one will will.

> 2)       Is there a way for this algorithm to determine which of the
> nodes was the one that had the problem?  A simple race to fence could
> result in the faulty server winning.

No, that's another problem with the two node option.  I think the new
quorum disk feature that's in the next release should address both of
these problems.

> Also is there a way to configure fence_ipmilan in cluster.xml to reboot
> rather than stop the server?  fence_ipmilan by itself takes the –o
> option (on,off,reboot)

Someone else can probably answer that.

Dave