[ClusterLabs] Antw: Re: questions about startup fencing

[Ulrich Windl]

> Adam Spiers <aspiers at suse.com> writes:
> 
>> - The whole cluster is shut down cleanly.
>>
>> - The whole cluster is then started up again.  (Side question: what
>>   happens if the last node to shut down is not the first to start up?
>>   How will the cluster ensure it has the most recent version of the
>>   CIB?  Without that, how would it know whether the last man standing
>>   was shut down cleanly or not?)
> 
> This is my opinion, I don't really know what the "official" pacemaker
> stance is: There is no such thing as shutting down a cluster cleanly. A
> cluster is a process stretching over multiple nodes - if they all shut
> down, the process is gone. When you start up again, you effectively have
> a completely new cluster.
> 
> When starting up, how is the cluster, at any point, to know if the
> cluster it has knowledge of is the "latest" cluster? The next node could
> have a newer version of the CIB which adds yet more nodes to the
> cluster.
> 
> The only way to bring up a cluster from being completely stopped is to
> treat it as creating a completely new cluster. The first node to start
> "creates" the cluster and later nodes join that cluster.

I think it is (once again) a problem of pacemaker: In HP Service Guard there
was a "cmhaltnode" to halt a node, and a "cmhaltcluster" (AFAIR) to halt the
whole cluster. The other direction was "cmrunnode" and "cmruncluster" (AFAIR).

So when doing it on the cluster level, all nodes end with the same information
(and can start with the "latest"...

> 
> Cheers,
> Kristoffer
> 
> -- 
> // Kristoffer Grönlund
> // kgronlund at suse.com 
> 
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