Hello, sorry, I forgot to mention 1 important point, we are not using DRDB but ext4 fs that are automatialy mounted by corosync as needed. We have a few services (with differents mount points) that run on those nodes and if 1 node fail, services get switched to remaining nodes. all 3 nodes can communicate to each other, I can ssh from one to another. Node3 see node1 and node2 (as pointed by corosync-objctl output) but don't join the existing ring, look like it create its own ring. The ring was working fine until I upgraded the os on node3. thanks, Mélanie On 07/26/2012 03:29 PM, Antonis Christofides wrote: > Hello, > > let me see if I've understood correctly. Assume the following cluster: > > > Internet Internet > | | > | | > node1 -------------- node2 > (drbd primary) (drbd secondary) > > Now the network is partitioned. node2 can't communicate with node1. So > it thinks node1 is down. So it makes itself a drbd primary, and clients > are now writing data to node2. But node1 is not really down, it's just > disconnected from node2. Some clients are still accessing node1 and > writing to it. Result: chaos. So we use stonith to guard against this > issue, but stonith requires a second, independent communication channel > to node1. I have no experience on this but I guess "independent" is a > big word. > > Instead: > > Internet Internet > | | > | | > node1 -------------- node2 > (drbd primary) (drbd secondary) > | | > | | > +-------- node3 ------+ > > > The network is partitioned; say node1 is disconnected from both node2 > and node3. Node1, seeing that it no longer has quorum (it is alone), > switches itself to drbd secondary. node2, seeing that node1 is no longer > there and that together with node3 it has a quorum, makes itself a drbd > primary. Yes, if you don't ignore quorum this is also fine. But at least do resource-level fencing in drbd do not allow an out-of-date node to be promoted. Nevertheless, without stonith you can't recover automatically from failures like stop-errors. Regards, Andreas -- Need help with Pacemaker/Corosync/DRBD? http://www.hastexo.com/now > > This looks to me simpler and easier to achieve (but again, I have no > experience). Isn't it a valid alternative solution, that makes stonith > unnecessary? I'm asking because in some places in the Pacemaker or drbd > documentation it says "don't do this without stonith!"; it doesn't say > "don't do this without either stonith or quorum!", and I was therefore > wondering whether I've understood something wrong. > _______________________________________________ > discuss mailing list > discuss@xxxxxxxxxxxx > http://lists.corosync.org/mailman/listinfo/discuss > _______________________________________________ discuss mailing list discuss@xxxxxxxxxxxx http://lists.corosync.org/mailman/listinfo/discuss
