On Fri, 2006-08-12 at 09:42 +0100, Andreas Pflug wrote:
> >   
> Can't this be accomplished right now by defining a global cluster for
> inter-site replication, and local clusters for intra-site traffic? Not a
> dream in terms of maintainability, but possible.
> 
It is certainly possible to daisy-chain replication from one cluster to
another.  Something like:

( A --> B )         -- cluster 1
      ( B --> C )   -- cluster 2

The problem with this is in performing swichovers.

In cluster 1 we can switchover once, but cannot switch back as the
replication triggers in database B for cluster 2 will be disabled.  We
could, I suppose re-enable those as part of a switchover procedure.

The bigger problem is in cluster 2, where there seems to be no
possibility at all of of performing a switchover.  To take database B
out of service for maintenance we would like to be able to simply
reconfigure the clusters into this:

( A --> C )         -- cluster 1
      ( C --> B )   -- cluster 2

but I see no way in slony to do this without rebuilding the entire
cluster.  Maybe using pgpool and some more manual procedures this would
be possible but it seems extremely fragile.

__
Marc
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