[Linux-cluster] 2-node tie-breaking

[Gordan Bobic]

Lon H. Hohberger wrote:

[...]

> 3.  Another simple way to do it is to use a fake "fencing agent" to
> introduce a delay:
> 
>    <fencedevice agent="/bin/sleep-10" name="sleeper" .../>
> 
> (where /bin/sleep-10 is something like:
> #!/bin/sh
> sleep 10
> exit 0
> )
> 
> Reference that agent as part of -one- node's fencing, and that node will
> lose by default.  This way, you don't have to set up qdiskd.  You could
> do the same thing by just editing the fencing agent directly on that
> node, as well - in which case, you wouldn't have to edit cluster.conf at
> all.

Funnily enough, this is exactly what I was just thinking about. Thanks. :-)

Unfortunately, things just got a bit more complicated for me, because it 
looks like my fencing device won't work. :-( Instead, it may have to end 
up being something as bodgy as ifdown-ing the cluster interface on the 
surviving node - in the 2 node scenario, that ought to be as good a 
using a managed switch based fencing device. The file systems will 
diverge if both nodes keep running, but neither fork will be corrupted.

Thinking about this a bit more, a tie-breaking IP ping may need to be 
implemented on the public and private NICs. On the public side, the 
tie-breaker would need to be the next router along. Are there hooks for 
implementing such a thing as a simple ping script, or heartbeat or 
similar that can be used to achieve this?

Thanks.

Gordan