Re: WAL logs multiplexing?

On Wed, 2005-12-28 at 16:38 +0000, Ian Harding wrote:
> On 12/28/05, Dmitry Panov <dmitry(at)tsu(dot)tula(dot)ru> wrote:
> > On Wed, 2005-12-28 at 11:05 -0500, Tom Lane wrote:
> > > Dmitry Panov <dmitry(at)tsu(dot)tula(dot)ru> writes:
> > > > Yes, but if the server has crashed earlier the script won't be called
> > > > and if the filesystem can't be recovered the changes will be lost. My
> > > > point is the server should write into both (or more) files at the same
> > > > time.
> > >
> > > As for that, I agree with the other person: a RAID array does that just
> > > fine, and with much higher performance than we could muster.
> > >
> >
> > Please see my reply to the other person. The other place can be on an
> > NFS mounted directory. This is what the Oracle guys do and they know
> > what they are doing (despite the latest release is total crap).
>
> RAID is great for a single box, but this option lets you have
> up-to-the-second PITR capability on a different box, perhaps at
> another site. My boss just asked me to set something like this up and
> the only way to do it at the moment is a replication setup which seems
> overkill for an offline backup.
>
> If this functionality existed, could it obviate the requirement for an
> archive_command in the simple cases where you just wanted the logs
> moved someplace safe (i.e. no intermediate compression or whatever)?
>

This functionality should have nothing to do with logs archiving. Think
of it as of a synchronous copy (or copies) of the pg_xlog directory:
files there are created, modified and removed at the same time. The
archiving is still done with the "archive_command" script which could
write it to a tape or do anything else you want.

This could be a nice feature which would made the "online" backup really
online. And it doesn't harm too, because if you don't need it you just
don't use it.

Best regards,
--
Dmitry O Panov | mailto:dmitry(at)tsu(dot)tula(dot)ru
Tula State University | Fidonet: Dmitry Panov, 2:5022/5.13
Dept. of CS & NIT | http://www.tsu.tula.ru/