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Subject: Re: High CPU usage (up to server hang) under heavy I/O load
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Mark Watts <m.watts@eris.qinetiq.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Mon, 16 Aug 2004 11:57:26 +0100
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On Llu, 2004-08-16 at 10:13, Mark Watts wrote:
> Would this also mean that if I stick a 64bit SATA raid card (a 3Ware 8506-4LP 
> in this case) into a 32bit pci slot, then I/O is always going to suck badly?
> 
> ... cos I do, and I/O sucks :)

Seperate issue.

64bit DMA is 64bit addressing (ie can DMA from above 4GB). 64bit wide
slot is double the speed for transfers. The 3ware 8xxx I thought could
do 64bit addressing although the driver seems to indicate it cannot,
so with over 4Gb it would hurt.