>>> digimer <li...@alteeve.ca> schrieb am 28.09.2018 um 19:11 in Nachricht <968d00cd-fad5-8f17-edfd-7787a9964...@alteeve.ca>: > On 2018-09-04 8:49 p.m., Ken Gaillot wrote: >> On Tue, 2018-08-21 at 10:23 -0500, Ryan Thomas wrote: >>> I’m seeing unexpected behavior when using “unfencing” – I don’t think >>> I’m understanding it correctly. I configured a resource that >>> “requires unfencing” and have a custom fencing agent which “provides >>> unfencing”. I perform a simple test where I setup the cluster and >>> then run “pcs stonith fence node2”, and I see that node2 is >>> successfully fenced by sending an “off” action to my fencing agent. >>> But, immediately after this, I see an “on” action sent to my fencing >>> agent. My fence agent doesn’t implement the “reboot” action, so >>> perhaps its trying to reboot by running an off action followed by a >>> on action. Prior to adding “provides unfencing” to the fencing >>> agent, I didn’t see the on action. It seems unsafe to say “node2 you >>> can’t run” and then immediately “ you can run”. >> I'm not as familiar with unfencing as I'd like, but I believe the basic >> idea is: >> >> - the fence agent's off action cuts the machine off from something >> essential needed to run resources (generally shared storage or network >> access) >> >> - the fencing works such that a fenced host is not able to request >> rejoining the cluster without manual intervention by a sysadmin >> >> - when the sysadmin allows the host back into the cluster, and it >> contacts the other nodes to rejoin, the cluster will call the fence >> agent's on action, which is expected to re-enable the host's access >> >> How that works in practice, I have only vague knowledge. > > This is correct. Consider fabric fencing where fiber channel ports are > disconnected. Unfence restores the connection. Similar to a pure 'off' > fence call to switched PDUs, as you mention above. Unfence powers the > outlets back up.
I doubt whether successful fencing can be emulated by "pausing" I/O: when re-establishing the fabric, outstanding I/Os might be performed (which cannot happen after real fencing). [...] Regards, Ulrich _______________________________________________ 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
