>>> "john tillman" <[email protected]> schrieb am 22.07.2021 um 16:48 in Nachricht <[email protected]>: > 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?
Maybe explain how it should work: If the two nodes cannot rech each other, but each can reach the ping node, which node has the quorum then? > > 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.htm > l >> 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 >>> <[email protected]‑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.htm > l >>> >>>> 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<[email protected]> 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/ _______________________________________________ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
