Date: Tue, 16 Feb 1999 15:15:09 -0500 (EST) From: "Robert G. Brown" <rgb@phy.duke.edu> To: aic7xxx Mailing List <AIC7xxx@freebsd.org> Cc: Doug Benjamin <dbenjamin@fnal.gov> Subject: Two controllers or a dual... Message-ID: <Pine.LNX.3.96.990216150406.14746A-100000@ganesh.phy.duke.edu>
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Dear List Humans:
We are trying to design systems intended to hold as much as 100-200 GB
of disk (to hold events collected at Fermilab and simulations thereof,
where the actual total dataset sizes can run into the terabyte range
quite easily).
A lot of the processing is likely to be disk I/O bound, and the question
has arisen -- is it better to get a single dual scsi controller (e.g.
the 7895) or two separate scsi controllers (e.g. 2940's)? Presumably
the dual controller will share an interrupt for both channels, and two
controllers would be on different interrupts. Does the answer depend on
whether or not the controllers are U, UW, U2W? I realize that 2 U2W
controllers will saturate the PCI bus anyway, but they should still give
some gain over a single U2W controller.
The system(s) in question will probably run linux, but the question
itself is open to anyone with either measurements (ideal) or theoretical
statements to make for either operating system.
Thank you,
rgb
P.S. -- if anyone wishes to comment on building the required disk out of
e.g. 3 or 4 Cheetahs per U2W controller vs buying a commercial disk
array (speed, cost comparisons, support in linux) that would be welcome
as well.
rgb
Robert G. Brown http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567 Fax: 919-660-2525 email:rgb@phy.duke.edu
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