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Date:	Sun, 4 Apr 2010 13:39:12 -0400
From:	tytso@....edu
To:	Pavel Machek <pavel@....cz>
Cc:	Ric Wheeler <rwheeler@...hat.com>,
	Krzysztof Halasa <khc@...waw.pl>,
	Christoph Hellwig <hch@...radead.org>, Mark Lord <lkml@....ca>,
	Michael Tokarev <mjt@....msk.ru>, david@...g.hm,
	NeilBrown <neilb@...e.de>, Rob Landley <rob@...dley.net>,
	Florian Weimer <fweimer@....de>,
	Goswin von Brederlow <goswin-v-b@....de>,
	kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, mtk.manpages@...il.com,
	rdunlap@...otime.net, linux-doc@...r.kernel.org,
	linux-ext4@...r.kernel.org, corbet@....net
Subject: Re: fsck more often when powerfail is detected (was Re: wishful
 thinking about atomic, multi-sector or full MD stripe width, writes in
 storage)

On Sun, Apr 04, 2010 at 03:47:29PM +0200, Pavel Machek wrote:
> > Yes, but ext3 does not enable barriers by default (the patch has been
> > submitted but akpm has balked because he doesn't like the performance
> > degredation and doesn't believe that Chris Mason's "workload of doom"
> > is a common case).  Note though that it is possible for dirty blocks
> > to remain in the track buffer for *minutes* without being written to
> > spinning rust platters without a barrier.
> 
> So we do wrong thing by default. Another reason to do fsck more often
> when powerfails are present?

Or migrate to ext4, which does use barriers by defaults, as well as
journal-level checksumming.  :-)

As far as changing the default to enable barriers for ext3, you'll
need to talk to akpm about that; he's the one who has been against it
in the past.

					- Ted
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