At 12:07 AM +0900 12/4/01, Takeshi Shibagaki wrote:
>Hi,
>
># You should not change CC list for everyone.
>
>From: ausias vives prat <ausias@jazzfree.com>
>Subject: Re: installing NetBSD on an IDE HD
>Date: Mon,  3 Dec 2001 13:05:59 +0100
>Message-ID: <20011203130601-r01010800-6d50a5b0-0911-0108@localhost>
>
>ausias> Finally I get it working.
>ausias> I realize that the ide performance is much slower than the 
>scsi, even with a ide
>ausias> drive faster than the scsi I used to work.
>
>Do you have a concrete example?
>
>Results of bonnie in following. I don't have recognized that the IDE
>performance is much slower than the SCSI one.
>
>Seagate ST34321A(IDE)4.3GB:
>               -------Sequential Output-------- ---Sequential Input-- 
>--Random--
>               -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- 
>--Seeks---
>Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU 
>/sec %CPU
>           100   610 94.9  1128 91.4   704 89.5   665 94.5  1270 87.2 
>61.4 36.9
>
>QUANTUM, FIREBALL ST3.2S, 0F0C(SCSI)3.2GB:
>               -------Sequential Output-------- ---Sequential Input-- 
>--Random--
>               -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- 
>--Seeks---
>Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU 
>/sec %CPU
>           100   676 94.2  1374 91.5   828 62.1   800 94.7  1926 89.6 
>82.3 32.6

That benchmark is doing one thing at a time. IDE is perfectly fine 
for that. The problem with IDE is that it does not support concurrent 
I/O. This is quite important for many un*x tasks, particularly if 
you're actually going to be touching swap space during use. As Un*x 
is designed as a multi-user, multi-tasking OS, concurrent I/O can 
play a crucial role in performance. This is what the original poster 
was getting at.

It *used* to be that IDE was slower primarily because it was so CPU 
intensive. In today's computers, however, the CPU's just sitting 
there doing nothing anyway, since they're so darn fast. Today, there 
are 2 main diifferences between SCSI and IDE.

1) The aforementioned concurrent I/O

2) SCSI drives are better quality than IDE. They are designed for 
server applications and are built to much higher specs. As my word is 
irrelevant ;-), a quick test would be to go to the website of any 
manufacturer that makes both (IBM for example) and look at the specs 
such as MTBF, duty cycle, etc. There is generally a fairly high 
discrepancy between the IDE offerings and the SCSI offerings.

HTH
Mike
-- 
Bikers don't *DO* taglines.