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Date: Thu, 5 Aug 2010 15:01:38 -0400
From: Chris Mason <chris.mason@oracle.com>
Subject: Re: direct-io regression [Was: How to track down abysmal
	performance ata - raid1 - crypto - vg/lv - xfs]
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To: Jeff Moyer <jmoyer@redhat.com>
Cc: Michael Monnerie <michael.monnerie@is.it-management.at>, linux-raid@vger.kernel.org, Valdis.Kletnieks@vt.edu, linux-kernel@vger.kernel.org, Dominik Brodowski <linux@dominikbrodowski.net>, xfs@oss.sgi.com, Christoph Hellwig <hch@infradead.org>, dm-devel@redhat.com, josef@redhat.com

On Thu, Aug 05, 2010 at 02:58:37PM -0400, Jeff Moyer wrote:
> Chris Mason <chris.mason@oracle.com> writes:
> 
> > But, I'm surprised your drive is doing 8K dio reads at 16MB/s, that
> > seems a little high.  
> 
> I'm not sure why you think that.  We're talking about a plain old SATA
> disk, right?  I can get 40-50MB/s on my systems for 8KB O_DIRECT reads.
> What am I missing?

Clearly I'm wrong, his drive is going much faster ;)  I expect the
smaller reads to be slower but the drive's internal cache is doing well.

-chris

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