Xref: utzoo unix-pc.general:3651 comp.sys.att:7432
Path: utzoo!utgpu!watmath!att!icus!lenny
From: lenny@icus.islp.ny.us (Lenny Tropiano)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Unix-pc steprate: some measurements...
Summary: Random seeks will give random results ...
Message-ID: <951@icus.islp.ny.us>
Date: 30 Aug 89 05:04:20 GMT
References: <1668@naucse.UUCP>
Reply-To: lenny@icus.islp.ny.us (Lenny Tropiano)
Organization: ICUS Software Systems, Islip, New York
Lines: 43

In article <1668@naucse.UUCP> sbw@naucse.UUCP (Steve Wampler) writes:
|>I've run Lenny's step rate exerciser on my system and thought
|>I'd post the results.
|>
..
Thanks, I'm interested, since you have a nice FAST drive on your
UNIX pc ...

|>External Drive   (maximum distance: 79,035,904)
|>
|>		Steprate 0			Steprate 14
|>long seeks:	    7				    5
|>random seeks:       2   			    3!
|>converging seeks:1510				  860!!
|>sequential seeks: 570				  570
|>
|>On the Swift, I'm assuming that the speed of random seeks is approaching
|>granularity.  I may run that again with more iterations sometime.  Note
|>that for the converging seeks test, the step rate gives a >40% improvement!
...
We have to realize that the random seek is just that, random.  Sometimes
you will get results that are better, sometimes you will get results that
are worse.  It really depends on how step-rate 0 and step-rate 14's random
numbers are ...  If, for instance, the step-rate 0 is small seeks (using
random) which take a minimal amount of time, and step-rate 14 are skewed
towards the long seeks, then it would show the results being worse for 
step-rate 14.   Not much can be extrapolated from the random seek, unless
the step-rate 14 was the same "RANDOM VALUES".   One could of course try
this ... srand(same-seed) each time would produce the same values,
I believe.

|>Thanks Lenny, for posting the program!  (And for the earlier posting
|>of ivfix!!)

You're welcome!   Glad to hear some brave soul tried the ivfix! :-)
I'm not as fortunate to have a drive with >1024 cylinders...

-Lenny
-- 
Lenny Tropiano             ICUS Software Systems         [w] +1 (516) 589-7930
lenny@icus.islp.ny.us      Telex; 154232428 ICUS         [h] +1 (516) 968-8576
{ames,pacbell,decuac,hombre,talcott,sbcs}!icus!lenny     attmail!icus!lenny
        ICUS Software Systems -- PO Box 1; Islip Terrace, NY  11752