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Message-ID: <20090325093913.GJ27476@kernel.dk>
Date: Wed, 25 Mar 2009 10:39:13 +0100
From: Jens Axboe <jens.axboe@...cle.com>
To: Jeff Garzik <jeff@...zik.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Arjan van de Ven <arjan@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Nick Piggin <npiggin@...e.de>, David Rees <drees76@...il.com>,
Jesper Krogh <jesper@...gh.cc>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.29
On Tue, Mar 24 2009, Jeff Garzik wrote:
> Linus Torvalds wrote:
>> But I really don't understand filesystem people who think that "fsck"
>> is the important part, regardless of whether the data is valid or not.
>> That's just stupid and _obviously_ bogus.
>
> I think I can understand that point of view, at least:
>
> More customers complain about hours-long fsck times than they do about
> silent data corruption of non-fsync'd files.
>
>
>> The point is, if you write your metadata earlier (say, every 5 sec) and
>> the real data later (say, every 30 sec), you're actually MORE LIKELY to
>> see corrupt files than if you try to write them together.
>>
>> And if you write your data _first_, you're never going to see
>> corruption at all.
>
> Amen.
>
> And, personal filesystem pet peeve: please encourage proper FLUSH CACHE
> use to give users the data guarantees they deserve. Linux's sync(2) and
> fsync(2) (and fdatasync, etc.) should poke the block layer to guarantee
> a media write.
fsync already does that, at least if you have barriers enabled on your
drive.
--
Jens Axboe
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