Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!snorkelwacker.mit.edu!ira.uka.de!fauern!faui43.informatik.uni-erlangen.de!csbrod
From: csbrod@immd4.informatik.uni-erlangen.de (Claus Brod)
Newsgroups: comp.periphs.scsi
Subject: Re: Seek-time controller dependent ???
Message-ID: <1991Mar28.120818.28142@informatik.uni-erlangen.de>
Date: 28 Mar 91 12:08:18 GMT
References: <1991Mar28.094427.4354@forwiss.uni-passau.de>
Distribution: comp
Organization: CSD., University of Erlangen, Germany
Lines: 33

gallersd@andorfer.fmi.uni-passau.de (Rainer Gallersdoerfer) writes:

>Last week I visited a friend who has got a 600MB SIEMENS hard disk.
>We installed it with different controllers ( WD7000FAAST2 and AHA1542B ).
>Surprisingly we measured different seek times with some standard test programs!
>I don't exactly remember but i think the 'track-to-track' ( average )
>times were 
>3.3ms ( 13.3ms ) for the WD and 6.7ms ( 16.7 ) for the AHA.
>HOW CAN THIS BE ???

Very well possible. I wrote a hard disk test program that is quite something
like a standard for the ATARI ST line. In an early version of it, I tested
seek times like this:
- send the controller a SEEK command
- isssue TEST UNIT READY commands to monitor if the seek is complete
- issue another SEEK and so on...

With older Seagate SCSI drives (ST157N, ST296N), this scheme failed totally.
I turned out that these drives are very slow in processing the TEST UNIT
READY command and thereby cluttered up the measured results. So it seems
very likely that the controllers used have an influence on seek times
measured by benchmark programs.

Naturally, this says nothing about the real performance of the hard disk,
especially because TEST UNIT READY commands are not used in standard
driver operations.

----------------------------------------------------------------------
Claus Brod, Am Felsenkeller 2,			Things. Take. Time.
D-8772 Marktheidenfeld, West Germany		(Piet Hein)
csbrod@medusa.informatik.uni-erlangen.de
Claus Brod@wue.maus.de
----------------------------------------------------------------------