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Date: Thu, 11 Nov 2010 10:43:52 +1100
From: Dave Chinner <david@fromorbit.com>
Subject: Re: 2.6.36 io bring the system to its knees
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>, dave b <db.pub.mail@gmail.com>, Sanjoy Mahajan <sanjoy@olin.edu>, Jesper Juhl <jj@chaosbits.net>, Chris Mason <chris.mason@oracle.com>, Ingo Molnar <mingo@elte.hu>, Pekka Enberg <penberg@kernel.org>, Aidar Kultayev <the.aidar@gmail.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Nick Piggin <npiggin@suse.de>, Arjan van de Ven <arjan@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Ted Ts'o <tytso@mit.edu>, Corrado Zoccolo <czoccolo@gmail.com>, Shaohua Li <shaohua.li@intel.com>, Steven Barrett <damentz@gmail.com>
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On Wed, Nov 10, 2010 at 07:59:10AM -0800, Linus Torvalds wrote:
> On Tue, Nov 9, 2010 at 5:32 PM, Dave Chinner <david@fromorbit.com> wrote:
> >
> > Don't forget to mention data=writeback is not the default because if
> > your system crashes or you lose power running in this mode it will
> > *CORRUPT YOUR FILESYSTEM* and you *WILL LOSE DATA*.
> 
> You will lose data even with data=ordered. All the data that didn't
> get logged before the crash is lost anyway.
> 
> So your argument is kind of dishonest. The thing is, if you have a
> crash or power outage or whatever, the only data you can really rely
> on is always going to be the data that you fsync'ed before the crash.
> Everything else is just gravy.

I crash kernels tens of times every day doing filesystem testing.
With data=ordered I have not seen a corrupted root filesystem as a
result of normal testing and crashing as long as I can remember.
With data=writeback, I'll have corrupted root ext3 partitions in
under a day. Hardly what I'd call stable or something you'd want
to deploy in production.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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