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From: Magnus Hagander <[email protected]>
To: Robert Haas <[email protected]>
Cc: Kevin Grittner <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: no universally correct setting for fsync
Date: Fri, 7 May 2010 16:03:55 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Fri, May 7, 2010 at 16:00, Robert Haas <[email protected]> wrote:
> On Fri, May 7, 2010 at 9:47 AM, Kevin Grittner
> <[email protected]> wrote:
>> Someone just posted to the -admin list with a database corrupted
>> while running with fsync=off.  I was all set to refer him to the
>> documentation explaining why he should stop doing this, but to my
>> surprise the documentation waffles on the issue way past what I
>> think is reasonable.
>>
>> http://www.postgresql.org/docs/8.4/interactive/runtime-config-wal.html#GUC-FSYNC
>>
>> There are dire-sounding statements interspersed with:
>>
>> | using fsync results in a performance penalty
>>
>> | Due to the risks involved, there is no universally correct setting
>> | for fsync.
>>
>> | If you trust your operating system, your hardware, and your
>> | utility company (or your battery backup), you can consider
>> | disabling fsync.
>>
>> Isn't this a little too rosy a picture to paint?
>
> I agree.  I've always thought this part of the documentation made
> setting fsync=off much more reasonable than I feel it to be.

+1, definitely. fsync=off should only be done if you *really*
understand what it means, and that requires a lot more explanation
than that...


-- 
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/

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