On 8/18/20 7:49 AM, Andrei Borzenkov wrote: > 17.08.2020 23:39, Jehan-Guillaume de Rorthais пишет: >> On Mon, 17 Aug 2020 10:19:45 -0500 >> Ken Gaillot <kgail...@redhat.com> wrote: >> >>> On Fri, 2020-08-14 at 15:09 +0200, Gabriele Bulfon wrote: >>>> Thanks to all your suggestions, I now have the systems with stonith >>>> configured on ipmi. >>> A word of caution: if the IPMI is on-board -- i.e. it shares the same >>> power supply as the computer -- power becomes a single point of >>> failure. If the node loses power, the other node can't fence because >>> the IPMI is also down, and the cluster can't recover. >>> >>> Some on-board IPMI controllers can share an Ethernet port with the main >>> computer, which would be a similar situation. >>> >>> It's best to have a backup fencing method when using IPMI as the >>> primary fencing method. An example would be an intelligent power switch >>> or sbd. >> How SBD would be useful in this scenario? Poison pill will not be swallowed >> by >> the dead node... Is it just to wait for the watchdog timeout? >> > Node is expected to commit suicide if SBD lost access to shared block > device. So either node swallowed poison pill and died or node died > because it realized it was impossible to see poison pill or node was > dead already. After watchdog timeout (twice watchdog timeout for safety) > we assume node is dead. Yes, like this a suicide via watchdog will be triggered if there are issues with thedisk. This is why it is important to have a reliable watchdog with SBD even whenusing poison pill. As this alone would make a single shared disk a SPOF, runningwith pacemaker integration (default) a node with SBD will survive despite ofloosing the disk when it has quorum and pacemaker looks healthy. As corosync-quorum in 2-node-mode obviously won't be fit for this purpose SBD will switch to checking for presence of both nodes if 2-node-flag is set.
Sorry for the lengthy explanation but the full picture is required to understand whyit is sufficiently reliable and useful if configured correctly. Klaus _______________________________________________ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
