[Info-vax] set cluster/expected_votes

[Michael Moroney]

JF Mezei <jfmezei.spamnot at vaxination.ca> writes:

>Malcolm Dunnett wrote:

>>   What it does is tells the other nodes to recompute quorum based on the
>> votes remaining in the cluster. I don't know if you consider this "much" 
>> or not, but it would seem to be precisely what is needed in this situation.

>It won't magically allow a cluster to continue to operate with fewer
>nodes than it had been designed to operate. AKA: you cannot cheat the
>minimums set by the sysgen expected_votes if I remember correctly.

The whole purpose of REMOVE_NODE is to allow the cluster to continue with
a configuration that would otherwise not have quorum.  There still may be
traps where REMOVE_NODE isn't a guarantee.  Consider the following: 3 node
cluster, each with 1 vote.  1 node is shut down (without REMOVE_NODE) or
crashes.  Now, VOTES=2, EXPECTED_VOTES=3.  Now shut down another node with
REMOVE_NODE.  If REMOVE_NODE removes its votes from both VOTES and
EXPECTED_VOTES (I'm not sure of the details offhand), the remaining system
will have 1 vote and EXPECTED_VOTES=2.  It will not have quorum and will
hang.  However, if you did a SET CLUSTER/EXPECTED_VOTES=2 beforehand,
you'll have both VOTES and EXPECTED_VOTES = 1 after the shutdown, and the
one node cluster will carry on.