linux-kernel - Re: RAID-1 performance under 2.4 and 2.6

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Message-ID: <47EC173F.4050309@tmr.com>
Date:	Thu, 27 Mar 2008 17:53:03 -0400
From:	Bill Davidsen <davidsen@....com>
To:	Bart Van Assche <bart.vanassche@...il.com>
CC:	Chris Snook <csnook@...hat.com>,
	Emmanuel Florac <eflorac@...ellique.com>,
	linux-kernel@...r.kernel.org
Subject: Re: RAID-1 performance under 2.4 and 2.6

Bart Van Assche wrote:
> On Tue, Mar 25, 2008 at 11:00 PM, Chris Snook <csnook@...hat.com> wrote:

>>  It means you shouldn't use dd as a benchmark.
> 
> If you want to benchmark write speed, you should add
> oflag=direct,dsync to the dd command line. For benchmarking read speed
> you should specify iflag=direct. Or, even better, you can use xdd with
> the flags -dio -processlock.
> 
No, you want your benchmark to measure performance doing what the 
application does. Do unless you have an application which has been 
heavily Linux-ized you don't want to measure something unrelated to the 
application requirements.

-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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