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Re: [Linux-cluster] IP-based tie-breaker on a 2-node cluster?



> It will assign the IPs to whatever interface already has an IP on that
> subnet. i.e. if your private cluster interface (crossover one) is
> 192.168.0.0/16 and your public interface is 10.0.0.0/8, you will have a
> resource group with IPs on the 10.0.0.0/8 subnet, not on the
> 192.168.0.0/16 subnet.

> You will probably want to add additional monitoring against switch port
> failures here, as otherwise if the switch port of the master node fails
> (it does happen, I've seen many a switch with just 1-2 dead ports),
> the backup will not notice as it can verify that the primary is up and
> responding, and it will not fence it and fail over to itself. You'd end up
> with a working cluster but unavailable service. IIRC there is a
> monitor_link option in the resource spec for this kind of thing.

Very informative post...thanks! The scenario you mentioned with a dead
switch port (or a single unplugged network cable, or whatever) is
something I had thought about, and I considered it to be a strike against
using a crossover cable. But, this "monitor_link" sounds like it might be
exactly what I've been looking for. I'll research that and see what I can
find.

You asked in your other post how I can tell the difference between a
network outage that should cause a fence and one that shouldn't. What I
wanted to do was set it up so that a node that can't reach the switch will
never try to fence the other node. That way, if the switch is down and
nobody can reach it, then nobody will fence. If there is a single port
failure and one node can still reach the switch, then it will fence the
other node and take over the services.

Thanks,

-Andrew L


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