[Linux-cluster] GFS 6.0 node without quorum tries to fence

[Steve Landherr]

In a netsplit, what does fencing achieve when done by a node that
doesn't have quorum?  It still won't have quorum.  It should probably
just clean up as best it can and leave the rest of the cluster alone.

-steve
--
Steve Landherr -- landherr at kazeon.com
Kazeon Systems, Inc.
Mountain View, California

-----Original Message-----
From: linux-cluster-bounces at redhat.com
[mailto:linux-cluster-bounces at redhat.com] On Behalf Of Michael Conrad
Tadpol Tilstra
Sent: Tuesday, August 03, 2004 9:13 AM
To: Discussion of clustering software components including GFS
Subject: Re: [Linux-cluster] GFS 6.0 node without quorum tries to fence

So looking at what you gave below, mitte was master. (making this guess
from the "Core lost slave quorum" part of the message below.)  It knows
that it doesn't have quorum, it still is going to try to be the Master.
It does not know "that it can not build a cluster."  The only thing it
knows right now about the other nodes is that they failed to send
heartbeats.  Therefor they must have left the cluter abnormally.
Therefor it must fence them.

The other two nodes see that mitte have failed to reply to heartbeats.
Therefor it must have left the cluster abnormally.  Therefor it must be
fenced.

Both sides of the netsplit are trying to resolve things to regain the
cluster.  From an outsiders view point (which you and I have, the nodes
do not.) We can see that mitte's attempts are futile, oben and unten
will get control of the cluter.  But the node cannot see this.

This is what makes netsplits kind of ugly.  

(using ifdown to test cluster stuff causes extra confusion in my
opinion. because you actually are creating a netsplit case.  Not a
simpler node down case.  The power switch is nice for this.)


I hope that made some sence.

-- 
Michael Conrad Tadpol Tilstra
Blood is thicker than water, and much tastier.