[Linux-cluster] 2-node tie-breaking

[gordan at bobich.net]

Thanks for that. How could this be hooked from cluster.conf? I wasn't 
planning to use the heartbeat stuff.

Gordan

On Thu, 7 Feb 2008, Brian Kroth wrote:

> A simple way might be to check for that case specifically and assign a
> preference to the node you want to win.  For instance:
>
> if $can_ping_internal_nodes \
> 	&& $can_ping_external_nodes \
> 	&& ! $can_ping_cluster_node; then
>
> 	if [ $HOSTNAME == node2 ]; then
> 		self_fence
> 	else
> 		steal_cluster_nodes_resources
> 	fi
> fi
>
> I know that you can do this via clever scoring in heartbeat [1], but I'm
> not sure about rgmanager.
>
> [1] linux-ha.org
>
> Brian
>
> gordan at bobich.net <gordan at bobich.net>:
>> Hi,
>>
>> I've got a slightly peculiar problem. 2-node cluster acting as a load
>> balanced fail-over router. 3 NICs: public, private, cluster.
>> Cluster NICs are connected with a cross-over cable, the other two are on
>> switches. The cluster NIC is only used for DRBD/GFS/DLM and associated
>> things.
>>
>> The failure mode that I'm trying to account for is the one of the cluster
>> NIC failing on one machine. On the public and privace networks, both
>> machines can still see everything (including each other). That means that a
>> tie-breaker based on other visible things will not work.
>>
>> So, which machine gets fenced in the case of the cluster NIC failure (or
>> more likely, if the x-over cable falls out)?
>>
>> Is there a sane, tested way to handle this condition? It would be quite
>> embarrasing if both, otherwise fully functional nodes, decided to shut
>> fence the other one off by shutting it down.
>>
>> Thanks.
>>
>> Gordan
>>
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>