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From: barel@imag.UUCP (Max BAREL)
Newsgroups: comp.sys.nsc.32k
Subject: ICM3216: speed of disk I/O
Message-ID: <1879@imag.UUCP>
Date: Tue, 28-Jul-87 10:40:51 EDT
Article-I.D.: imag.1879
Posted: Tue Jul 28 10:40:51 1987
Date-Received: Thu, 30-Jul-87 06:51:22 EDT
Reply-To: barel@imag.UUCP (Max BAREL)
Distribution: world
Organization: IMAG, University of Grenoble, France
Lines: 27
Keywords: disk driver, SCSI.

Since my last posting generate some useful answers, let's try again.
When we get our ICM machine, we were quit happy but disapointed by speed of
disk I/O. 
I wrote a simple benchmark, doing random BLOCK read on /dev/dsk/0s7, in order to
minimise the buffer cache mechanism influence. This test ends up with a
throughput of 10 kbyte/s.
Our hard was:
	-emulex controller
	-CDC wren II 85 Mb disk
The same test on an ATT 3b2/400 give 30Kb/s.
I recently change the emulex cont. for an Adaptec RLL 2/7. This speed up
the speed to 15Kb/s.
Here is the question: What is slow in the chain?
The ICM SCSI channel and the controler are specified for much more.
We try other disk (hitachi,...), whithout succes.
All have raisonable seek time.
The driver could be the problem ?
I hear my modest bench fly to NSC, which get much better result. It seem it is
with a new release of the driver.
I should welcome some light around this, since I can't believe the driver
was so bad.
Thank's.

-- 
-------------------------
Max Barel
barel@imag.UUCP