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Re: [Linux-cluster] Re: CS5 two-nodes with quorum disk



On Wed, 2007-12-19 at 11:52 +0100, Alain Moulle wrote:
> Hi Lon
> 
> Many thanks for your last both responses, it's much clearer
> in my head now ... ;-)
> 
> When you speak of "a method to enable master-set-wins (e.g. for
> operation w/o heuristics)" , will it be delivered by a patch when
> ready ? or just a matter in configuration file ?

It will be both.

The current idea is to use a quasi-"fence agent" which talks to qdiskd.
Basically, "fence_qdisk" asks qdiskd "Am I in the master set?"  - if we
are not, qdiskd "fencing" fails immediately.  This "fencing" operation
needs to happen before other fence agents.

If we /are/ in the master set, we flip the "dead" node/partition's state
on the quorum disk S_EVICT (Evicted) - which will (probably) cause the
node to die, and return success to fenced.  At this point, normal
fencing occurs.

This provides also a quick "not supported for production use without
other 'real' fencing" test agent, too...

The limitation is that you cannot use multiple fence methods - or if you
do, you must reference the fence_qdisk agent from all methods.


> if patch, when do you think it could be available ? because
> I'm interested ... I guess it will be sort of a way to establish
> that one of the two-nodes cluster is master and in case of
> "perfect symmetrical splits", it is always the master the winner ...
> if so, that will be fine for me .

Yes, that's the intent - I'm also thinking about methods of how to
simplify things somewhat.  If you have input, let me know. :)

-- Lon


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