CTDB - the 'Mainz' plan for clustered Samba
idra at samba.org
Sun Oct 1 19:30:11 GMT 2006
On Mon, 2006-10-02 at 05:17 +1000, tridge at samba.org wrote:
> > 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.
This triggers another question I had in mind.
What happen if an unresponsive server comes up before the recovery is
finished (same question if one node goes down during recovery)?
We need to start a new recovery phase of course, but is it ok to do so
at any moment? Even during another recovery?
> It's quite important that VNNs not remain the same after a recovery.
Yes, this was perfectly clear.
> 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.
Ok, this is what I needed to hear.
> 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.
Do we have any real statistic do back this?
What will happen in the worst case scenario?
Samba Team GPL Compliance Officer
email: idra at samba.org
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