Two controllers or a dual...

[Robert G. Brown]

On Wed, 17 Feb 1999, Doug Ledford wrote:

> The U2W controllers and disks have made a *massive* difference in
> performance tests I have performed.  Additionally, there is at least one
> non-official patch I recommend for large memory systems that makes a
> major difference to disk read speeds.  Using a PII-400 dual machine, two
> U2W channels, two Seagate Cheetah 9GB disks per channel, all four disks
> having a stripe in a RAID0 array.  The per char portion of a bonnie test
> was in the range of 15 to 20MB/s both in and out, the block output was
> around 65MB/sec, the block input was about 60MB/sec before the patch and
> 73.8MB/s consistent after the patch.  Note that 73.8MB/s was consistent
> because it was the maximum media speed of those four cheetahs in the
> area of the stripes.  So, since I went from being CPU bound at 62MB/s to
> disk bound at 73.8MB/s, I don't know the real speedup I got, but it was
> significant :)  However, having noted the benefit, here's the catch.  It
> only effects machines with 256MB of RAM or more.  This machine had 512MB
> of RAM.  A larger machine would see a greater impact.

Bless you!  Numbers!

> I've had good luck with things such as using a single controller that
> has dual Ultra2 channels (the 3950U2B or 3950U2D) and then loading up
> around 3 or 4 Cheetah drives per channel.  If nothing else, the LVD bus
> is worth the upgrade to U2W regardless of the speed issues.  You'll get
> flaky busses out of SE in a heartbeat of cable length, but on my
> personal LVD bus here at home, I have a 10' external 68pin cable that
> runs from my computer to my drive tower, and then inside the drive tower
> I have about 6' or 7' of additional cable, then an external terminator. 
> I tested that exact bus as a SE bus and it blew up instantly, but as LVD
> I've never had a problem with it.  That's in the range of 5m of bus. 
> I've still got a good 7m of leeway to work with as well :)  I should
> also note that I got all the cabling and the drive tower from Stay
> OnLine in RTP so it's all locally accessible to you at least Robert :)

A reply that is worth its wait in gold.  Or worth the beer I have to
add to the sixpack or two I already owe you, payable at this year's
Expo in Raleigh if we don't connect sooner than that:-) We have an
account at StayOnline, so this is all very easy to negotiate.  We'll
probably get the system(s) itself at Intrex as I'm trying hard to
establish a relationship with a local vendor with a repair shop and they
are willing to work with me on microconfiguration.

Thanks immensely,

          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 at phy.duke.edu





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