CTDB - the 'Mainz' plan for clustered Samba

[tridge at samba.org]

Simo,

 > Ok, but at all effects what this will mean is that the LMASTER for most
 > of the keys will change, is this a desirable effect?

yes, it's desirable :)

See this bit:

 1) the recovery process needs to assign every node a new VNN, and
    will choose VNNs that are different from all the VNNs currently in
    use. This is important to ensure that none of the old VNNs remain
    valid, so we can detect when a 'zombie' node that is
    non-responsive during recovery starts sending messages again. When
    such a node wakes up it will trigger a CTDB_ERR_VNN_MAP message as
    soon as it tries to send a CTDB message.

It's quite important that VNNs not remain the same after a recovery.

I also don't mind if the recovery takes a few seconds. It should be a
rare event, and having to redistribute the data during a recovery is a
small cost. Trying to optimise for the "startup" case after a recovery
just isn't worth doing. The important thing is to make the normal
"running" case fast.

Also remember that the total amount of records in these databases
tends to be small. It might be a few thousand on a moderately busy
box, but it won't be billions. That means that redistributing data on
a fast network is trivial.

Cheers, Tridge