Date: Mon, 16 Jul 2007 16:02:11 -0500
From: "Jim C. Nasby" <decibel@decibel.org>
To: Hannes Dorbath <light@theendofthetunnel.de>
Cc: Gregory Stark <stark@enterprisedb.com>,
	pgsql-performance@postgresql.org
Subject: Re: FORGOT TO CONFIGURE RAID!       DELL POWEREDGE 2950
Message-ID: <20070716210210.GZ39272@nasby.net>
References: <1184357777.135345.38110@n60g2000hse.googlegroups.com>
	<46988951.9050108@theendofthetunnel.de>
	<87tzs7b93w.fsf@oxford.xeocode.com>
	<4698A347.2020401@theendofthetunnel.de>
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On Sat, Jul 14, 2007 at 12:19:51PM +0200, Hannes Dorbath wrote:
> Gregory Stark wrote:
> >> From the DELL site it seems this `PERC 5/i' on board controller
> >> (assuming that's what you have) doesn't even have a BBU. If you don't
> >> plan to post here in a few weeks again about data corruption, go out a=
nd
> >> shop a serious controller.
> >=20
> > This is a bit of a strange comment. A BBU will improve performance but
> > Postgres doesn't require one to guarantee data integrity.
> >=20
> > If your drives have write caching disabled (ie write-through) and your
> > controller does write-through caching and you leave fsync=3Don and
> > full_page_writes=3Don which is the default then you shouldn't have any =
data
> > integrity issues.
>=20
> That was my point, controllers without BBU usually leave drive caches
> turned on, as with drive caches off performance would be unbearable bad.

Wow, are you sure about that? I've never heard it before, but that'd be
pretty disturbing if it's true...
--=20
Jim Nasby                                      decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

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