From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)
Date: Thu, 29 May 2008 12:22:23 +0100
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To: Bill Davidsen <davidsen@tmr.com>
Cc: Jens =?UTF-8?B?QsOkY2ttYW4=?= <jens.backman@gmail.com>, Justin Piszcz <jpiszcz@lucidpixels.com>, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, xfs@oss.sgi.com
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> I really don't think that's any part of the issue, the same memory and 
> bridge went 4-5x faster in other read cases. The truth is that the 
> raid-1 performance is really bad, and it's the code causing it AFAIK. If 
> you track the actual io it seems to read one drive at a time, in order, 
> without overlap.

Make sure the readahead is set to be a fair bit over the stripe size if
you are doing bulk data tests for a single file. (Or indeed in the real
world for that specific case ;))