[Info-vax] set cluster/expected_votes

[JF Mezei]

Malcolm Dunnett wrote:

>    If you use the "remove node" option when you shut the two systems 
> down the quorum should automatically adjust to the remaining system.

"remove node" doesn't do much. It just signals the other nodes not to
expect this one to come back (I think this consists of an expected votes).


I am not sure exactly what the "set clu/expected_votes" does.  But I had
been told previously that it was basically useless in small clusters.

The sysgen parameter EXPECTED_VOTES is really "minimum acceptable votes
to continue", at least during the boot process. (aka: a quorum is
calculated form expected_votes and node cannot continue to boot until
this quorum has been reached as other nodes join).

I ***ASSUME*** (please correct me if wrong) that when there is a cluster
transition, each node uses its sysgen "expected_votes" as a guide to
whether the new quorum is acceptable or not. (or perhaps the highest
"expected_votes" value taken from the remaining nodes is used to
calculate whether the new quorum would be above or below the one
calculated by Expected_votes.

If you have 3 nodes with 1 vote each, the quorum is 2, so it doesn't
matter if you remove 1 node, shut it down, crash it or disconnect it,
the 2 other nodes will survive.

But if the 3rd node has 5 votes, and all nodes have SYSGEN
EXPECTED_VOTES=7 (1+1+5), then I am not sure the nodes A and B with each
1 vote would survive when their expected_votes in sysgen say minimum
acceptable quorum is 4.