Ken Gaillot <kgail...@redhat.com> writes: >>> I think it works differently: One task periodically reads ist mailbox slot >>> for commands, and once a comment was read, it's executed immediately. Only >> if >>> the read task does hang for a long time, the watchdog itself triggers a >> reset >>> (as SBD seems dead). So the delay is actually made from the sum of "write >>> delay", "read delay", "command excution". > > I think you're right when sbd uses shared-storage, but there is a > watchdog-only configuration that I believe digimer was referring to. > > With watchdog-only, the cluster will wait for the value of the > stonith-watchdog-timeout property before considering the fencing successful.
I think there are some important distictions to make, to clarify what SBD is and how it works: * The original SBD model uses shared storage as its fencing mechanism (thus the name Shared-storage based death) - when talking about watchdog-only SBD, a new mode only introduced in a fork of the SBD project, it would probably help avoid confusion to be explicit about that. * Watchdog-only SBD relies on quorum to avoid split-brain or fence loops, and thus requires at least three nodes or an additional qdevice node. This is my understanding, correct me if I am wrong. Also, this disqualifies watchdog-sbd from any of Digimers setups since they are 2-node only, so that's probably something to be aware of in this discussion. ;) * The watchdog fencing in SBD is not the primary fence mechanism when shared storage is available. In fact, it is an optional although strongly recommended component. [1] [1]: We (as in SUSE) require use of a watchdog for supported configurations, but technically it is optional. -- // Kristoffer Grönlund // kgronl...@suse.com _______________________________________________ Users mailing list: Users@clusterlabs.org http://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
