[ClusterLabs] Failure of preferred node in a 2 node cluster

Wei Shan weishan.ang at gmail.com
Sat Apr 28 21:19:40 EDT 2018


I'm using Redhat Cluster Suite 7with watchdog timer based fence agent. I
understand this is a really bad setup but this is what the end-user wants.

ATB => auto_tie_breaker

"When the auto_tie_breaker is used in even-number member clusters, then the
failure of the partition containing the auto_tie_breaker_node (by default
the node with lowest ID) will cause other partition to become inquorate and
it will self-fence. In 2-node clusters with auto_tie_breaker this means
that failure of node favoured by auto_tie_breaker_node (typically nodeid 1)
will result in reboot of other node (typically nodeid 2) that detects the
inquorate state. If this is undesirable then corosync-qdevice can be used
instead of the auto_tie_breaker to provide additional vote to quorum making
behaviour closer to odd-number member clusters."


On Sun, 29 Apr 2018 at 02:15, Digimer <lists at alteeve.ca> wrote:

> On 2018-04-28 09:06 PM, Wei Shan wrote:
> > Hi all,
> >
> > If I have a 2 node cluster with ATB enabled and the lowest node ID node
> > has failed. What will happen? My assumption is that the higher node ID
> > node will self fence and be rebooted. What happens after that?
> >
> > Thanks!
> >
> > --
> > Regards,
> > Ang Wei Shan
> Which cluster stack is this? I am not familiar with the term "ATB".
> If it's a standard pacemaker or cman/rgmanager cluster, then on node
> failure, the good node should block and request a fence (a lost node is
> not allowed to be assumed gone via self fence, except when using a
> watchdog timer based fence agent). If the fence doesn't work, the
> survivor should remain blocked (better to hang than risk corruption). If
> the fence succeeds, then the survivor node will recover any lost
> services based on the configuration of those services (usually a simple
> (re)start on the good node).
> --
> Digimer
> Papers and Projects: https://alteeve.com/w/
> "I am, somehow, less interested in the weight and convolutions of
> Einstein’s brain than in the near certainty that people of equal talent
> have lived and died in cotton fields and sweatshops." - Stephen Jay Gould

Ang Wei Shan
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