linux-kernel - Re: SATA Harddisk speed drop of 100 MB/s

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Message-ID: <20070625151841.GK10008@csclub.uwaterloo.ca>
Date:	Mon, 25 Jun 2007 11:18:41 -0400
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	Carlo Wood <carlo@...noe.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Arjan van de Ven <arjan@...radead.org>,
	Jeff Garzik <jeff@...zik.org>, linux-kernel@...r.kernel.org
Subject: Re: SATA Harddisk speed drop of 100 MB/s

On Sat, Jun 23, 2007 at 04:59:06AM +0200, Carlo Wood wrote:
> Just one kernel version? The problem here is in every
> kernel revision after 551c012d7eea3dc5ec063c7ff9c718d39e77634f
> 
> 2.6.20-rc2,rc3,rc4,rc5,rc6,rc7 ... 2.6.20 ... 2.6.21 ... 2.6.22-rc5
> 
> noop:
>  Timing buffered disk reads:  254 MB in  3.00 seconds =  84.66 MB/sec
> 
> anticipatory:
>  Timing buffered disk reads:  252 MB in  3.02 seconds =  83.43 MB/sec
> 
> deadline:
>  Timing buffered disk reads:  258 MB in  3.02 seconds =  85.41 MB/sec
> 
> cfq:
>  Timing buffered disk reads:  194 MB in  3.03 seconds =  64.06 MB/sec
> 
> The normal value is cfq. So, all other schedulars are somewhat faster,
> but still far from the correct 165 MB/s.

How do you know 165MB/s is correct?

As for 10k rpm being faster, well remember rotation speed _and_ areal
density is what gives transfer rate.  a 750GB 7200rpm is likely able to
have a higher throughput than a 73GB 10k rpm drive since more bits pass
by the head in any given unit of time on the larger drive.  The 7200 rpm
has a slower average access time though.

--
Len Sorensen
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