Subject: Re: Out-of-order writing by disk drives
From: Chris Mason <chris.mason@oracle.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Michael Tokarev <mjt@tls.msk.ru>, Mark Lord <lkml@rtr.ca>,
       Anton Ertl <anton@mips.complang.tuwien.ac.at>,
       linux-kernel@vger.kernel.org
In-Reply-To: <20090414185058.GZ14687@one.firstfloor.org>
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	 <20090414185058.GZ14687@one.firstfloor.org>
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Date: Tue, 14 Apr 2009 15:27:06 -0400
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On Tue, 2009-04-14 at 20:50 +0200, Andi Kleen wrote:
> On Tue, Apr 14, 2009 at 10:09:48PM +0400, Michael Tokarev wrote:
> > Andi Kleen wrote:
> > []
> > >Where I see it as a problem is with virtualization; LVM seems to be the
> > >most sane way to manage file systems for lots of VMs and you likely
> > >want barriers there too.
> > 
> > Virtualisation is the best fit for partitionable raid1 arrays.
> > It is, in fact, what we have here -- I tested LVM but rejected
> > it because of this very issue - it does not support barriers.
> 
> It does now as of 2.6.29, as long as you only have a single
> underlying device and use dm linear.

Eric Sandeen noticed this is actually still broken:

http://lkml.org/lkml/2009/3/23/360

-chris


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