Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On 08/30/2011 11:25 AM, William Seligman wrote: > On 8/29/11 4:42 PM, Digimer wrote: >> On 08/29/2011 03:36 PM, William Seligman wrote: >>> A general question: I have a Corosync+Pacemaker with DRBD setup on Linux; I'll >>> give the details if it's relevant. Corosync+Pacemaker controls DRBD start, stop, >>> and promotion. I've implemented fencing via STONITH as Corosync resources. >>> >>> I have not put fencing in the drbd.conf file; I was under the impression that >>> Corosync+Pacemaker would take of STONITHing a node if there's a DRBD problem. Is >>> this correct? Or should I have fencing/STONITH configured in both Corosync and >>> drbd.conf? >>> >>> Does the answer change between a primary/secondary versus dual-primary setup? >> >> You still want to configure fencing, but you can use the >> 'crm-fence-peer.sh' handler. Using this with 'resource-and-stonith' will >> tell DRBD to block I/O until the fence succeeds, preventing it from >> going dual-primary (even if just for the brief moment between fault and >> fence). > > I may be dense, but I find the answer ambiguous; perhaps I didn't ask the > question the right way. > > Let me ask in a differen way: If I have fencing set up in corosync, and corosync > controls drbd, do I also need fencing in drbd.conf? Yes you do. There is the potential for a period of time between the fault and it's detection by Pacemaker. During this time, if DRBD is not appropriately configured, both sides could go StandAlone/Primary. Once that happens, you've got a split-brain. The 'crm-fence-peer.sh' is used in drbd.conf to let DRBD block IO and call a fence via pacemaker. This will result in two fence calls, which is obviously overkill, but that isn't what we're after. The corresponding "resource-and-stonith" argument is what matters. That is what will block IO at the DRBD level until the fence call succeeds. -- Digimer E-Mail: digimer at alteeve.com Freenode handle: digimer Papers and Projects: http://alteeve.com Node Assassin: http://nodeassassin.org "At what point did we forget that the Space Shuttle was, essentially, a program that strapped human beings to an explosion and tried to stab through the sky with fire and math?"