[DRBD-user] Handling unresolvable split-brain in dual-primary setup with pacemaker

Joschi Brauchle joschi.brauchle at tum.de
Fri Apr 15 14:25:50 CEST 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hey everyone,

I have some questions about handling unresolvable split-brains in a dual-
primary setup with pacemaker.


This is the scenario:
 - DRBD and pacemaker are configured to start resource r0 in dual-primary mode
 - For test reasons, a split-brain between node1 and node2 is created, that is 
not automatically resolvable
 - Thus, DRDB disconnects the resource r0 after all configured automatic 
resolvers failed.
So far so good.


This is the problem:
 - Although DRDB disconnects the resource due to the split-brain, pacemaker 
doesn't get to know about this condition at all, because both nodes are in 
"cs:StandAlone ro:Primary/Unknown" state.


My questions are:
1) Is resource level fencing the solution (also in a dual-primary setup)?
2) is there any documentation out there on the "crm-fence-peer.sh" script?
3) Is the "crm-fence-peer.sh" also working in a dual-primary setup?
4) What I would like to happen is that BOTH nodes stay in "slave" mode and do 
not get promoted to "primary" after the disconnect. I don't want pacemaker to 
continue starting other resources in disconnected DRBD state! Is there any way 
to do this with the "crm-fence-peer.sh" handler?

Thanks for any help!
--
Dipl.-Ing. Joschi Brauchle, M.Sc.

Institute for Communications Engineering (LNT)
Technische Universitaet Muenchen (TUM)
80290 Munich, Germany

Tel (work): +49 89 289-23474
Fax (work): +49 89 289-23490
E-mail: joschi.brauchle at tum.de
Web: http://www.lnt.ei.tum.de/



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