[Pacemaker] new doc about stonith/fencing

[Peter Kruse]

Hi Dejan,

Dejan Muhamedagic wrote:
> Never worked with PDUs, but there should be a difference compared
> to the lights-out devices: if a PDU looses power then all nodes
> connected to it do as well. I suppose that that is much more
> likely than only one outlet failing. In that case all cluster is
> down and you have other things to worry about rather than fencing.

we usually use two PDUs, one for each node.  But even then, if
one loses power (and with it one of the nodes) the resources
will not migrate, which is the very problem here.

>> This would be true if the PDU (and with it the host) loses power.
>> > At the moment it looks that stonith without such an algorithm is
>> > a SPoF by design, because after a single failure (powerloss), the
>> > cluster is not able to bring up the resources again.

> This is something certainly worth looking at. On the other side,
> it's not really so difficult or pricey to devise a setup where
> you won't have to worry about this detail.

really?  can we talk about it?  Maybe that would be a good addition
to the doc.

Regards,

   Peter