Re: FreeBSD Softupdates??

From: Alfred Perlstein <bright(at)wintelcom(dot)net>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Neil Conway <nconway(at)klamath(dot)dyndns(dot)org>, PostgreSQL General List <pgsql-general(at)postgresql(dot)org>
Subject: Re: FreeBSD Softupdates??
Date: 2000-09-26 15:38:08
Message-ID: 20000926083808.V9141@fw.wintelcom.net
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* Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> [000926 07:12] wrote:
> -- Start of PGP signed section.
> > On Tue, Sep 26, 2000 at 03:20:31AM -0700, Alfred Perlstein wrote:
> > > It can cause problems because softupdates makes meta data changes
> > > (in this case file creation/removal) asyncronously, the same actually
> > > happens with most other logging filesystems that don't support
> > > transactions.
> >
> > I've been running FreeBSD 4.1 with soft updates on my development box
> > for a while now without any problems at all. Although it's not
> > production so there's not a lot of load on PgSQL.
> >
> > I don't know if it hurts or hampers performance.
>
> Good question. I can see soft updates improving performance because it
> flushes meta-data writes all at once, rather than each time a file is
> created/destroyed. I don't see any downside for PostgreSQL. The
> default fsync() will still work, or at least it should. This is not the
> same as mounting a volume as async.

You are correct, softupdates will honour a fsync and stabilize the
file (make sure it's a round if you have a crash).

--
-Alfred Perlstein - [bright(at)wintelcom(dot)net|alfred(at)freebsd(dot)org]
"I have the heart of a child; I keep it in a jar on my desk."

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