On 2019-02-11 6:34 a.m., Maciej S wrote: > I was wondering if anyone can give a plain answer if fencing is really > needed in case there are no shared resources being used (as far as I > define shared resource). > > We want to use PAF or other Postgres (with replicated data files on the > local drives) failover agent together with Corosync, Pacemaker and > virtual IP resource and I am wondering if there is a need for fencing > (which is very close bind to an infrastructure) if a Pacemaker is > already controlling resources state. I know that in failover case there > might be a need to add functionality to recover master that entered > dirty shutdown state (eg. in case of power outage), but I can't see any > case where fencing is really necessary. Am I wrong? > > I was looking for a strict answer but I couldn't find one... > > Regards, > Maciej
Fencing is as required as a wearing a seat belt in a car. You can physically make things work, but the first time you're "in an accident", you're screwed. Think of it this way; If services can run in two or more places at the same time without coordination, you don't need a cluster, just run things everywhere. If you need coordination though, you need fencing. The role of fencing is to force a node that has entered into an unknown state and force it into a known state. In a system that requires coordination, often times fencing is the only way to ensure sane operation. Also, with pacemaker v2, fencing (stonith) became mandatory at a programmatic level. -- 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 _______________________________________________ Users mailing list: Users@clusterlabs.org https://lists.clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org