[ClusterLabs] Antw: question about dc-deadtime

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Fri Dec 16 03:26:45 EST 2016

>>> Chris Walker <christopher.walker at gmail.com> schrieb am 15.12.2016 um 21:00 in
<CAFD1iUqfXLLChWiAc8iHK9T+C9rV44k-8JUk8bY+C6aw6nR1gQ at mail.gmail.com>:
> Hello,
> I have a quick question about dc-deadtime.  I believe that Digimer and
> others on this list might have already addressed this, but I want to make
> sure I'm not missing something.
> If my understanding is correct, dc-deadtime sets the amount of time that
> must elapse before a cluster is formed (DC is elected, etc), regardless of
> which nodes have joined the cluster.  In other words, even if all nodes
> that are explicitly enumerated in the nodelist section have started
> Pacemaker, they will still wait dc-deadtime before forming a cluster.
> In my case, I have a two-node cluster on which I'd like to allow a pretty
> long time (~5 minutes) for both nodes to join before giving up on them.
> However, if they both join quickly, I'd like to proceed to form a cluster
> immediately; I don't want to wait for the full five minutes to elapse
> before forming a cluster.  Further, if a node doesn't respond within five
> minutes, I want to fence it and start resources on the node that is up.

I don't know the details of pacemaker, but in HP-UX ServiceGuard there was a "cluster formation timeout". As far as I understood that it was used when all cluster nodes reboot, avoiding the situation that a cluster will be built wit some nodes, then others joining withing a few seconds. So the cluster would wait for nodes until "forming the cluster" (one could also want a cluster to form once some minimum number of nodes is ready to join). However once a cluster is fomed, any new node would immediately join the existing cluster. Is that what you want?

> With Pacemaker/Heartbeat, the initdead parameter did exactly what I want,
> but I don't see any way to do this with Pacemaker/Corosync.  From reading
> other posts, it looks like people use an external agent to start HA daemons
> once nodes are up ... is this a correct understanding?
> Thanks very much,
> Chris

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