[Linux-cluster] Quorum Disk question

[Lon Hohberger]

On Wed, 2007-03-07 at 16:36 +0000, James Lapthorn wrote:
> Good afternoon,
> 
> Hopefully somebody can help with a Quorum disk question I have.  I have a
> 4 node cluster and have adopted a 'last man standing' approach.  Because
> of this I use a quorum disk which is I have setup on my SAN.
> 
> I have added the following configuration into my cluster.conf file.
> 
> <quorumd device="/dev/vpathe" interval="1" tko="10" votes="4">
>      <heuristic interval="2" program="ping leoukldb1 -c1 -t1" score="     
>     1"/>
>      <heuristic interval="2" program="ping leoukldb2 -c1 -t1" score="     
>     1"/>
>      <heuristic interval="2" program="ping leoukldb3 -c1 -t1" score="     
>     1"/>
>      <heuristic interval="2" program="ping leoukldb4 -c1 -t1" score="     
>     1"/>
> </quorumd>
> 
> Each node has 1 vote and the quorum disk has 4, therefore Quorum should
> remain if 3 nodes are removed from the cluster.
> 
> While testing this I have noticed that i get the following error in the log:
> 
>  qdiskd[26676]: <notice> Score insufficient for master operation (1/2;
> max=4); downgrading
> 
> At this point Activity is blocked.
> 
> Is this to do with my heuristic programs, should I not ping each memeber
> node and maybe ping something like 'localhost'

Yes, that's the problem.  Try one heuristic with a big score and pinging
the closest router.

Note that if you have any unreliable parts of the network with the
RHEL4U4 Qdisk, you may experience false 'downgrades' (bad).

If you have a current CVS update of RHEL4/STABLE/RHEL5/etc., you can run
with no heuristics at all - which will be a "last-man-standing"
approach.

Additionally, the 'false downgrade' problem will be fixed in RHEL4U5
(and is fixed in CVS) by adding 'tko' counts to the heuristics.

I have updated cman / cman-kernel packages which have several qdisk
fixes here (including the two above):

http://people.redhat.com/lhh/packages.html

-- Lon