[ClusterLabs] Prevent Corosync Qdevice Failback in split brain scenario.
jfriesse at redhat.com
Thu Jan 2 08:30:15 EST 2020
> Hi ,
> I am planning to use Corosync Qdevice version 3.0.0 with corosync version 2.4.4 and pacemaker 1.1.16 in a two node cluster.
> I want to know if failback can be avoided in the below situation.
> 1. The pcs cluster is in split brain scenario after a network break between two nodes. But both nodes are visible and reachable from qdevice node.
> 2. The qdevice with ffsplit algorithm selects node with id 1 (lowest node id) and node 1 becomes quorate.
> 3. Now if node 1 goes down/is not reachable from qdevice node , the node 2 becomes quorate.
> But when node 1 becomes again reachable from qdevice , it becomes quorate and node 2 again goes down. i.e The resources failback to node 1.
> Is there any way to prevent this failback.
No on the qdevice/qnetd level (or at least not generic solution - it is
possible to set tie_breaker to node 2, so resources wouldn't be then
shifted for this specific example, but it is probably not what was
I can imagine to have an algorithm option so qnetd would try to keep
active partition active as long as other requirements are fulfilled - so
basically add one more test just before calling tie-breaker.
Such option shouldn't be hard to implement and right now I'm not aware
about any inconsistencies which may it bring.
> With Regards
> Somanath Thilak J
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