From owner-freebsd-hackers  Thu Apr 11 11:45:20 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.3/8.7.3) id LAA00726
          for hackers-outgoing; Thu, 11 Apr 1996 11:45:20 -0700 (PDT)
Received: from labinfo.iet.unipi.it (labinfo.iet.unipi.it [131.114.9.5])
          by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id LAA00703
          for <freebsd-hackers@FreeBSD.org>; Thu, 11 Apr 1996 11:44:35 -0700 (PDT)
Received: from localhost (luigi@localhost) by labinfo.iet.unipi.it (8.6.5/8.6.5) id UAA15330; Thu, 11 Apr 1996 20:34:19 +0200
From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Message-Id: <199604111834.UAA15330@labinfo.iet.unipi.it>
Subject: Re: HDD cpu usage (IDE vs. SCSI).
To: toor@dyson.iquest.net (John S. Dyson)
Date: Thu, 11 Apr 1996 20:34:18 +0200 (MET DST)
Cc: se@zpr.uni-koeln.de, bde@zeta.org.au, dutchman@spase.nl,
        freebsd-hackers@FreeBSD.org
In-Reply-To: <199604101308.IAA00947@dyson.iquest.net> from "John S. Dyson" at Apr 10, 96 08:08:34 am
X-Mailer: ELM [version 2.4 PL23]
Content-Type: text
Sender: owner-hackers@FreeBSD.org
X-Loop: FreeBSD.org
Precedence: bulk

Sorry for not trimming the message too much but the numbers sound
strange.

> NCR-SCSI driver ASUS SC200 W/ST12400 2.1GB Hawk
> Command overhead is 1370 usec (time_4096 = 2093, time_8192 = 2815)
> transfer speed is 5.6707e+06 bytes/sec
> Command overhead is 839 usec (time_4096 = 2093, time_8192 = 3347)
> transfer speed is 3.26577e+06 bytes/sec

First I assume you measure the overhead as

    t4K - (t8K - t4K)

but the numbers for the NCR probably suggest that data ought to be
averaged over a larger number of experiments.

Second, I guess you are measuring the SCSI/IDE/EIDE bus transfer speed,
rather than the disk transfer speed, isn't it ?
Also, how comes that a 2X CDROM has such a low speed ?

> SCSI 2.2X CDROM
> Command overhead is 5655 usec (time_4096 = 9033, time_8192 = 12410)
> transfer speed is 1.21281e+06 bytes/sec
> Command overhead is 5670 usec (time_4096 = 9046, time_8192 = 12422)
> transfer speed is 1.21324e+06 bytes/sec

Third, what do you mean by "Standard IDE" vs EIDE ? Isn't it rather an
ISA vs. VLB/PCI comparison ? I have tried both a WDC540 and a WDC1.6GB,
and the 540 gets a maximum speed (with iozone or bonnie) of some
2.2MB/s at most, no matter how fast is the interface or the system. 

Instead, the WDC 1.6GB (as you also experienced) is rated at 5.5MB/s on
the same system).

> Standard IDE W/WDC540H
> Command overhead is 436 usec (time_4096 = 2001, time_8192 = 3565)
> transfer speed is 2.61859e+06 bytes/sec
> Command overhead is 436 usec (time_4096 = 2002, time_8192 = 3568)
> transfer speed is 2.61586e+06 bytes/sec
> 
> EIDE W/WDC540H
> Command overhead is 375 usec (time_4096 = 814, time_8192 = 1254)
> transfer speed is 9.31994e+06 bytes/sec
> Command overhead is 368 usec (time_4096 = 800, time_8192 = 1231)
> transfer speed is 9.49095e+06 bytes/sec
> 
> EIDE W/WDC 1.6GB
> Command overhead is 217 usec (time_4096 = 513, time_8192 = 809)
> transfer speed is 1.38444e+07 bytes/sec
> Command overhead is 196 usec (time_4096 = 502, time_8192 = 808)
> transfer speed is 1.33987e+07 bytes/sec

	Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================