Hi,

From: "Michael G. Schabert" <mikeride@mac.com>
Subject: Re: installing NetBSD on an IDE HD
Date: Mon, 3 Dec 2001 11:17:54 -0500
Message-ID: <p05100301b8315470a5b0@[192.168.1.4]>

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

What do you call for "concurrent I/O".

mikeride> It *used* to be that IDE was slower primarily because it was so CPU 
mikeride> intensive. In today's computers, however, the CPU's just sitting 
mikeride> there doing nothing anyway, since they're so darn fast. Today, there 
mikeride> are 2 main diifferences between SCSI and IDE.
mikeride> 
mikeride> 1) The aforementioned concurrent I/O
mikeride> 
mikeride> 2) SCSI drives are better quality than IDE. They are designed for 
mikeride> server applications and are built to much higher specs. As my word is 
mikeride> irrelevant ;-), a quick test would be to go to the website of any 
mikeride> manufacturer that makes both (IBM for example) and look at the specs 
mikeride> such as MTBF, duty cycle, etc. There is generally a fairly high 
mikeride> discrepancy between the IDE offerings and the SCSI offerings.

It is a general theory, but in this case, I don't think so.
In port-mac68k, SCSI is pseudo DMA after all, so CPU time in SCSI
is same to IDE almostly. port-mac68k isn't port-i368(for example).

And 2) is also a general theory. Today, IDE driver is more
popular than SCSI driver. So I think both are equal quality.

# I allow SCSI hardware is better than IDE one, but case by case.

Takeshi Shibagaki
ie9t-sbgk@asahi-net.or.jp