On Wed, Jun 15, 2011 at 03:26:56PM -0500, mark - pacemaker list wrote: > On Wed, Jun 15, 2011 at 12:24 PM, imnotpc <imno...@rock3d.net> wrote: > > > > > What I was thinking is that the DC is never fenced > > > Is this actually the case?
In a way it is true. Only DC can order fencing and there is always exactly one DC in a partition. On split brain, each partition elects a DC and if the DC has quorum it can try to fence nodes in other partitions. That's why in two-node clusters there's always a shoot-out. But note that the old DC (before split brain), if it loses quorum, gets fenced by a new DC from another partition. > It would sure explain the one "gotcha" I've > never been able to work around in a three node cluster with stonith/SBD. If > you unplug the network cable from the DC (but it and the other nodes all > still see the SBD disk via their other NIC(s)), the DC of course becomes > completely isolated. It will fence Fence? It won't fence anything unless it has quorum. Do you have no-quorum-policy=ignore? Thanks, Dejan > one of the still good nodes right away, > and the surviving node that still has network connectivity will become DC. > So, you have two DCs, the original one which is disconnected from the > network and your newly elected one (not really elected, just took over > because it's the last host left that has network). When the just-fenced > node comes back up, you get quorum with the new DC and your disconnected DC > finally gets shot. > > For any non-DC node, you get exactly the behavior you'd expect, where > unplugging its network cable gets it fenced and everyone else stays happy. > I'd hoped for a situation where unplugging the DC would have the other two > say, "well, our DC is gone, but we can see each other so he need to be > fenced". Maybe I've just missed a necessary timeout setting somewhere to > delay the isolated DC from fencing a good node so quickly? > > Sorry, I guess that's a thread hijack, but I've looked and googled and never > anywhere been able to find something that says DCs don't get fenced, so this > has confused me for a bit. > > Regards, > Mark > _______________________________________________ > Pacemaker mailing list: Pacemaker@oss.clusterlabs.org > http://oss.clusterlabs.org/mailman/listinfo/pacemaker > > Project Home: http://www.clusterlabs.org > Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf > Bugs: > http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker _______________________________________________ Pacemaker mailing list: Pacemaker@oss.clusterlabs.org http://oss.clusterlabs.org/mailman/listinfo/pacemaker Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker
