17-May-2005

Calculating VOTES
Just an idea....
When both Io and Daphne leave the cluster, Diana will recognize "quorum loss" and therefopre suspend all processing (even signalling the fact...). So, to prevent this, quorum loss is to be prevented. But how...
Well, if Diana would have so much votes that quorum is not lost! It's the algorithm used by VMS, that gives the answer:
Quorum is calculated as the maximum of the next calculations:
On boot: Estimated quorum = (EXPECTED_VOTES + 2)/2 Rounded down
On entering, or leaving the cluster: QUORUM = (total of all VOTES + 2)/2 Rounded down
The last calculated quorum (when a node has left the cluster) is observed as well.

If the current number of cluster votes drops below the quorum value (because of computers leaving the cluster) , the system will hang.

So: If Diana gets VOTES = Sum of the votes of all other members + 1, would that be good?

DIANA gets VOTES = 3, the others get VOTES = 1. EXPECTED_VOTES would be 3 + 1 + 1 = 5 on all.
So quorum, on boot, would be 5 + 2 /2, = 3 for all. Diana would run, and Io nor Daphne would, unless Diana is running (so they can join the cluster). But Diana would still have quorum if both Io and Daphne would leave the cluster. Just what is requested.

To have Io and Daphne run - stand-alone, or in a cluster of themselves, would require a second scheme. No problem: define [SYS1] and configure this in there...

Will try this....