Shahaf Abileah a écrit :
I just read this page:
http://www.postgresql.org/docs/8.2/static/continuous-archiving.html
And it made me wonder whether this mechanism of continuous archiving and
point-in-time recovery (PITR) can be used for replication. In other
words, Postgres already generates write-ahead-log files for all
operations. If you can transmit those files to another machine and
replay them, continuously, then you have a form of replication.
But, it’s not clear if this is possible. The article linked above talks
about doing continuous archiving, but it doesn’t talk about doing
continuous recovery. Instead, it talks about doing a single
point-in-time recovery. Moreover, this recovery requires the target
(“slave”) machine to be offline during the recovery process.
Continuous recovery is possible, see :
http://www.postgresql.org/docs/8.2/static/warm-standby.html
But you're right, during the recovery the slave is not available for
connections.
Does anyone know whether it’s possible to use Postgres’ archiving and
PITR for replication?
Yes, it's called Log Shipping or Warm Server Standby.
By the way, if it can, it seems that:
1. It would have the advantage that various operations are handled
in a more natural manner than with Slony (e.g. DDL)
2. It would have the disadvantage that you can’t be choosy about
what to replicate – you get the entire DB cluster, or nothing at all.
Is that correct?
Yes.
Regards.
--
Guillaume.
http://www.postgresqlfr.org
http://dalibo.com
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