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Date:      Mon, 25 Aug 2003 21:20:46 -0700
From:      Sean Chittenden <sean@chittenden.org>
To:        Rod Taylor <rbt@rbt.ca>
Cc:        Paul Pathiakis <paul@pathiakis.com>
Subject:   Re: Tuning Postgresql on FreeBSD 5.1
Message-ID:  <20030826042046.GC1514@perrin.nxad.com>
In-Reply-To: <1061869321.3193.9.camel@jester>
References:  <200308250929.32143.paul@pathiakis.com> <20030826030527.GB1514@perrin.nxad.com> <1061869321.3193.9.camel@jester>

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> > while still maintaining reasonable file system performance (ext2 is
> > faster than ext3 by a wide margin, but ext2 is _not_ a reliable FS).
>=20
> > > #fsync =3D true
> >=20
> > Change this to false.
>=20
> This is a funny thing to suggest after the filesystem comment.

:) Did you enjoy that?  :) I should clarify that piece of "advice"
though.

If you're _sure_ power isn't going to fail (using a UPS) and make
regular backups (standard operating procedure), then fsync =3D false
can be a good thing in terms of performance (roughly speaking, it
doubles performance of any write/update operation).  A disk failure is
a disk failure and there is no substitute for RAID.  Leaving stability
in the OS and PostgreSQL... this is a FreeBSD mailing list, stability
goes without saying.  :) That said though, if you're unable to stomach
the possibility of possibly loosing data when one of the above fails,
keep fsync =3D true.  If, however, you have mitigated the risks to
levels that your business/operation is comfortable with (your data
center is on generators, your DB systems have UPSs, are using RAID,
and make frequent backups), then I would set fsync =3D false for most
noncritical apps (non-financial, non-medical).

-sc

--=20
Sean Chittenden

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