[Linux-cluster] fenced(8) not fencing through all fenceing devices

[David Teigland]

On Thu, Feb 01, 2007 at 06:50:36PM +0100, Miroslav Zubcic wrote:
>         <clusternodes>
>                 <clusternode name="tan9f1" votes="1">
>                         <fence>
>                                 <method name="1">
>                                         <device name="pwr01" port="1"
> switch="10.52.2.240"/>
>                                 </method>
>                                 <method name="2">
>                                         <device name="pwr02" port="1"
> switch="10.52.2.241"/>
>                                 </method>
>                         </fence>

I think you want something like this instead:

<fence>
	<method name="1">
		<device name="pwr01" option="off" port="1" ../>
		<device name="pwr02" option="off" port="1" ../>
		<device name="pwr01" option="on" port="1" ../>
		<device name="pwr02" option="on" port="1" ../>
	</method>
</fence>

There are two problems with your config:

1. You have both devices in separate methods.  A second method is only
tried if the first fails.  

2. You're using the default "reboot" option which isn't reliable with dual
power supplies.  The first port may come back on before the second is
turned off.  So, you need to turn both ports off (ensuring the power is
really off) before turning either back on.

You may still have a minor problem, though, because in the two-node
cluster mode, a cluster partition will result in both nodes trying to
fence each other in parallel.  With a single power supply this works fine
because one node will always be turned off before it can turn off the
other.  But, with dual power supplies you can get both nodes turning off
one power port on the other, although only one of the nodes should succeed
in turning off the second power port.  i.e. the winner of the fencing race
may end up with one of its power ports turned off.  Whether this is a big
problem, I don't know.

Dave