[ClusterLabs] questions about startup fencing

[Klaus Wenninger]

On 11/29/2017 04:23 PM, Kristoffer Grönlund wrote:
> 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 have a newer version of the CIB which adds yet more nodes to the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.

To make it even clearer imagine a node being reverted
to a previous state by recovering it from a backup.

Regards,
Klaus

>
> 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.
>
> Cheers,
> Kristoffer
>