From owner-freebsd-performance@FreeBSD.ORG  Tue Jul 22 09:06:58 2003
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Date: Tue, 22 Jul 2003 12:06:56 -0400 (EDT)
From: David Miller <small@d.sparks.net>
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To: Dan Langille <dan@langille.org>
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cc: freebsd-database@freebsd.org
cc: freebsd-performance@freebsd.org
cc: Jason Stone <freebsd-performance@dfmm.org>
Subject: Re: Tuning for PostGreSQL Database
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On Tue, 22 Jul 2003, Dan Langille wrote:

> On 21 Jul 2003 at 20:35, Jason Stone wrote:
> 
> > I feel like this is an extremely important point.  If softupdates changes
> > the semantics of sync(2)/fsync(2), then it absolutely has to be off for a
> > postgresql server because postgresql counts on fsync in order to make its
> > durability guarantees.
> 
> If this means all FreeBSD-PostgreSQL users need to change their 
> setup, we need to do something ASAP.  I'd first recommend getting the 
> confirmation from the PostgreSQL team, then adjusting the PostgreSQL 
> documenation and the FreeBSD port.

If softupdates breaks the semantics of sync/fsync it affects a lot more
than postgres, it affects every application that manages data on its
own.  Every other database that doesn't do raw IO would seem to be
affected, for example.

Before we go off half-cocked, can anyone confirm that softupdates actually
does this - reorders/delays sync/fsync - on writes within a file?  I had
the impression it worked on meta data about files (directory structures) 
rather than the data within the file itself.

--- David