From: Bernd Helmle <mailings@oopsware.de>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
To: Andrew Dunstan <andrew@dunslane.net>
Cc: pgsql-hackers@postgresql.org
Subject: Re: no universally correct setting for fsync
Date: Sat, 08 May 2010 01:32:59 +0200
Message-ID: <A1EBC6E5100210B51612365E@amenophis> (raw)
In-Reply-To: <4BE3E205020000250003138F@gw.wicourts.gov>
References: <4BE3D3930200002500031382@gw.wicourts.gov>
<4BE425F7.30804@dunslane.net>
<4BE3E205020000250003138F@gw.wicourts.gov>
--On 7. Mai 2010 09:48:53 -0500 Kevin Grittner
<Kevin.Grittner@wicourts.gov> wrote:
> I think it goes beyond "tweaking" -- I think we should have a bald
> statement like "don't turn this off unless you're OK with losing the
> entire contents of the database cluster." A brief listing of some
> cases where that is OK might be illustrative.
>
+1
> I never meant to suggest any statement in that section is factually
> wrong; it's just all too rosy, leading people to believe it's no big
> deal to turn it off.
I think one mistake in this paragraph is the passing mention of
"performance". I've seen installations in the past with fsync=off only
because the admin was pressured to get instantly "more speed" out of the
database (think of "fast_mode=on"). In my opinion, phrases like
"performance penalty" are misleading, if you need that setting in 99% of
all use cases for reliable operation.
I've recently even started to wonder if the performance gain with fsync=off
is still that large on modern hardware. While testing large migration
procedures to a new version some time ago (on an admitedly fast storage) i
forgot here and then to turn it off, without a significant degradation in
performance.
--
Thanks
Bernd
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Subject: Re: no universally correct setting for fsync
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