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Date: Sun, 4 Apr 2010 13:39:12 -0400
From: tytso@mit.edu
To: Pavel Machek <pavel@ucw.cz>
Cc: Ric Wheeler <rwheeler@redhat.com>, Krzysztof Halasa <khc@pm.waw.pl>,
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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)
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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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