Re: RAID0 and pg_xlog

From: Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>
To: smarlowe(at)g2switchworks(dot)com
Cc: jnasby(at)pervasive(dot)com, zhouqq(at)cs(dot)toronto(dot)edu, pgsql-general(at)postgresql(dot)org
Subject: Re: RAID0 and pg_xlog
Date: 2005-09-10 03:08:25
Message-ID: 20050910.120825.71085811.ishii@sraoss.co.jp
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> > On Fri, Sep 09, 2005 at 06:20:21PM -0500, Scott Marlowe wrote:
> > > > pgpool is a connection pool; it has (almost) nothing to do with
> > > > replication. It certainly doesn't work to provide any kind of data
> > > > security on a RAID0 setup.
> > > >
> > > > I'm not arguing against anything people have suggested, only pointing
> > > > out that if you're using RAID0 your data is not safe against a drive
> > > > failure, except possible using pgcluster (some would argue that
> > > > statement-based replication isn't as reliable as log-based).
> > >
> > > Um. No. It has a synchronous replication mode, which I've used, and it
> > > works quite well.
> > >
> > > Look it up, it's pretty cool. Writes to both pg machines synchronously,
> > > reads from them load balanced. Of course, there are some limits imposed
> > > by this methodology, re: things like random() and such.
> > >
> > > Now, if you're arguing against statement based replication, that I can
> > > understand. but pgpool can definitely do two box sync replication.
> >
> > Oh, I didn't realize that. Though I have to wonder why they duplicated
> > what pgcluster provides...
>
> I doubt it's as good as pgcluster. It's simple dual machine sync
> replication. I think it was a case of being 95% there when the pooling
> part was done, so why not just toss in replication for good measure.

As a developer of pgpool I have to admit above. If it's technically
possible, why not chalenge it? That's a nature of an engineer:-)

BTW, some codes(probably the connection pooling part) in PGCluster
have been copied from pgpool. Instead I have been getting good
feedbacks/bug fixes from the author of PGCluster. It is kind of a
collaboration work, and I think this is one of the greatest thing with
open source softwares.
--
SRA OSS, Inc. Japan
Tatsuo Ishii

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