[Info-vax] Wide area cluster, metro area network, seeking info

[Mark Berryman]

On 6/12/21 1:01 AM, Phillip Helbig (undress to reply) wrote:
> In article <sa11hi$cpc$1 at dont-email.me>, Mark Berryman
> <mark at theberrymans.com> writes:
> 
>> First, I recommend you ignore the suggestions to add a 3rd node to your
>> cluster.  In your situation, it is not really a viable answer.
> 
> It would solve most of the problems you mention below, and also could
> serve as a test node.
> 
>> There are configurations that will allow a member of a 2-node cluster to
>> automatically continue in the event that the other node fails.
> 
> How?  If one has more votes, it is essential.  If the votes are the
> same, both are essential.  Unless you mean a quorum disk.  But it should
> be at a third location.
> 

Situation: two separate nodes with no shared storage

Configure each node with one vote.  Configure each node to use a local 
disk as the quorum disk, also with one vote.

As the cluster is formed, the nodes will discover that they do not agree 
on the quorum disk and will exclude it, resulting in quorum being 
established with the 2 votes provided by the nodes.

One node goes down, the other pauses while it recomputes quorum.  In 
doing so it discovers there is no longer a conflict regarding the quorum 
disk so it includes it, resulting in two votes which re-achieves quorum 
and the node continues.

When the failed node comes back up, the quorum disks will be excluded 
again and the cluster will return to its original state.  The danger of 
this configuration is that, if the communication channel between the two 
nodes is lost but the nodes remain up, the cluster will partition.  This 
is addressed in my original posting.

Mark Berryman