There was a lot of discussion on this topic which might have overshadowed this question so I will ask it again in case someone missed it.
It comes from a post (see below) that we were pointed to here by Andrei: Is there something like the described "ping tiebreaker" in the current world of pacemaker/corosync? Best Regards, -John > Interesting read. Thank you for providing it! > > In this follow up post > https://techthoughts.typepad.com/managing_computers/2007/10/more-about-quor.html > the author mentions the following: > > Ping tiebreaker > > Some HA systems provide a ping tiebreaker. To make this work, you pick a > address outside the cluster to ping, and any partition that can ping that > address has quorum. The obvious advantage is that it's very simple to set > up - doesn't require any additional servers or shared disk. The > disadvantage (and it's a big one) is that it's very possible for multiple > partitions to think they have quorum. In the case of split-site (disaster > recovery) type clusters, it's going to happen fairly often. If you can > use this method for a single site in conjunction with fencing, then it > will likely work out quite well. It's a lot better than no tiebreaker, or > one that always says "you have quorum". Having said that, it's > significantly inferior to any of the other methods. > > The quote "It's a lot better than no tiebreaker..." is what I am looking > for. Is there something like a "ping tiebreaker" in the current world of > pacemaker/corosync? > > Thanks to all those who have already commented on my question. I > appreciate the input/education. > > Best Regards, > -John > > > >> On Wed, Jul 21, 2021 at 3:55 PM Ulrich Windl >> <ulrich.wi...@rz.uni-regensburg.de> wrote: >>> >>> Hi! >>> >>> Maybe someone feels motivated to write some article comparing the >>> concepts >>> * split brain >>> * quorum >>> * fencing >>> >> >> Yet another one? Using your own reply "search is free". >> >> https://techthoughts.typepad.com/managing_computers/2007/10/split-brain-quo.html >> >>> There are eight possible states that I tried to illustrate on the >>> attached sketch (S="Split Brain", "Q=Quorum, F=Fencing). >>> >>> ;-) >>> >>> Regards, >>> Ulrich >>> >>> >>> >>> Andrei Borzenkov 21.07.2021, 07:52 >>> >>> >>> On 21.07.2021 07:28, Strahil Nikolov via Users wrote: >>> > Hi, >>> > consider using a 3rd system as a Q disk. >>> >>> What was not clear in "Quorum is a different concept and doesn't remove >>> the need for fencing"? >>> >>> > Also, you can use iscsi from that node as a SBD device, so you will >>> have proper fencing .If you don't have a hardware watchdog device, you >>> can use softdog kernel module for that. >>> > Best Regards,Strahil Nikolov >>> > >>> > >>> > On Wed, Jul 21, 2021 at 1:45, Digimer<li...@alteeve.ca> wrote: On >>> 2021-07-20 6:04 p.m., john tillman wrote: >>> >> Greetings, >>> >> >>> >> Is it possible to configure a two node cluster (pacemaker 2.0) >>> without >>> >> fencing and avoid split brain? >>> > >>> > No. >>> > >>> >> I was hoping there was a way to use a 3rd node's ip address, like >>> from a >>> >> network switch, as a tie breaker to provide quorum. A simple >>> successful >>> >> ping would do it. >>> > >>> > Quorum is a different concept and doesn't remove the need for >>> fencing. >>> > >>> >> I realize that this 'ping' approach is not the bullet proof solution >>> that >>> >> fencing would provide. However, it may be an improvement over two >>> nodes >>> >> alone. >>> > >>> > It would be, at best, a false sense of security. >>> > >>> >> Is there a configuration like that already? Any other ideas? >>> >> >>> >> Pointers to useful documents/discussions on avoiding split brain >>> with >>> two >>> >> node clusters would be welcome. >>> > >>> > https://www.alteeve.com/w/The_2-Node_Myth >>> > >>> > (note: currently throwing a cert error related to the let's encrypt >>> > issue, should be cleared up soon). >>> > >>> > >>> > _______________________________________________ >>> > Manage your subscription: >>> > https://lists.clusterlabs.org/mailman/listinfo/users >>> > >>> > ClusterLabs home: https://www.clusterlabs.org/ >>> > >>> >>> _______________________________________________ >>> Manage your subscription: >>> https://lists.clusterlabs.org/mailman/listinfo/users >>> >>> ClusterLabs home: https://www.clusterlabs.org/ >>> >>> _______________________________________________ >>> Manage your subscription: >>> https://lists.clusterlabs.org/mailman/listinfo/users >>> >>> ClusterLabs home: https://www.clusterlabs.org/ >> _______________________________________________ >> Manage your subscription: >> https://lists.clusterlabs.org/mailman/listinfo/users >> >> ClusterLabs home: https://www.clusterlabs.org/ >> >> > > > _______________________________________________ > Manage your subscription: > https://lists.clusterlabs.org/mailman/listinfo/users > > ClusterLabs home: https://www.clusterlabs.org/ > > _______________________________________________ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
