Re: Seeking datacenter PITR backup procedures [RESENDING]

On Aug 19, 2007, at 7:23 AM, Bill Moran wrote:
>> Assumptions:
>> a. After pg_stop_backup(), Pg immediately recycles log files and
>> hence wal
>> logs can be copied to backup. This is a clean start.
>
> I don't believe so.  ARAIK, all pg_stop_backup() does is remove the
> marker that pg_start_backup() put in place to tell the recovery
> process
> when the filesystem backup started.

I'm pretty certain that's not the case. For a PITR to ensure that
data is back to a consistent state after a recovery, it has to replay
all the transactions that took place between pg_start_backup and
pg_stop_backup; so it needs to know when pg_stop_backup() was
actually run.

> By not backing up pg_xlog, you are
> going to be behind by however many transactions are in the most recent
> transaction log that has not yet been archived.  Depending on how
> often
> your databases are updated, this is likely acceptable.  If you need
> anything more timely than that, you'll probably want to implement
> Slony or some other replication system.

Just keep in mind that Slony is *not* a backup solution (though you
could possibly argue that it's log shipping is).
--
Decibel!, aka Jim Nasby                        decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)