[Pacemaker] new doc about stonith/fencing

[Dejan Muhamedagic]

Hi,

On Wed, May 13, 2009 at 03:50:58PM +0200, Peter Kruse wrote:
> 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.

Why not use one PDU for both nodes?

>>> 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.

Use a UPS. Or blades with single power infrastructure. I'd opt
for one of these two.

Thanks,

Dejan

> Regards,
>
>   Peter
>
>
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