From mboxrd@z Thu Jan  1 00:00:00 1970
From: Richard Scobie <richard@sauce.co.nz>
Subject: Re: Poor RAID5 performance on new SMP system
Date: Mon, 18 Oct 2004 16:44:20 +1300
Sender: linux-raid-owner@vger.kernel.org
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Marc wrote:
> Hi,
> I recently upgraded my file server to a dual AMD 2800+ on a Tyan Tiger MPX 
> motherboard. The previous server was using a PIII 700 on an Intel 440BX 
> motherboard. I basically just took the IDE drives and their controllers 
> across to the new machine. The strange thing is that the RAID-5 performance 
> is worse than before! Have a look at the stats below:

Hi Marc,

Unfortunately you have a lemon :(

I spent some time trying to get acceptable performance out of an Adaptec 
SCSI RAID 0 on the 32 bit, 33MHz bus of one of these boards and 
eventually found this:

http://forums.2cpu.com/showthread.php?s=c8040a4e9c9b6390dd389f1b3cca32de&threadid=31211&perpage=15

The executive summary is

"After testing AMD determined that the problem was identified as a 
bandwidth issue(this was startling information). It appears that the 
motherboard has a bandwidth limitation of 25MB/s on PCI devices that are 
connected through the AMD 768 Southbridge."

This was in line with my findings.

I have not tried, but it is possible that a 64 bit 66MHz IDE card will 
be OK.

Regards,

Richard