RE: Looking for the cause of poor I/O performance

Some systems may have 66 MHz PCI, or 64 bit.
Or, just more than 1 PCI bus.  My desktop system has 3 PCI buses, I think.

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org
[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Mark Hahn
Sent: Monday, December 06, 2004 4:35 PM
To: TJ
Cc: linux-raid@vger.kernel.org
Subject: Re: Looking for the cause of poor I/O performance

quoted

for comparison, a fairly crappy SiS 735-based k7 system with
64b-wide PC2100 can deliver maybe 1.2 GB/s dram bandwidth.
hdparm -T is about 500 MB/s, and would probably have trouble
breaking 200 MB/s with raid0 even if it had enough buses.

an older server of mine is e7500-based, dual xeon/2.4's, with
2xPC1600 ram.  it sustains about 1.6 GB/s on Stream, and about
500 MB/s hdparm -T, and can sustain 250 MB/s through it's 6-disk
raid without any problem.

hmmm.. In these cases, how does the throughput exceed the PCI bandwidth?

Do 

these boards have multiple busses? PCI-X?

I didn't say they exceeded bus bandwidth ("if it had enough").
the latter does actually have multiple buses, some of which are pcix;
that's pretty common among server boards.

interestingly, even non-server desktop parts can exceed PCI bandwidth - 
I did a disk server a few years ago that used two chipset ATA ports
and an add-in 4-port card to hit about 150 MB/s total (sustained).

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