Date: Sun, 07 Sep 1997 23:23:52 -0700 From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@MindBender.serv.net> To: Greg Lehey <grog@lemis.com> Cc: Drew Derbyshire <ahd@kew.com>, Ollivier Robert <roberto@keltia.freenix.fr>, current@freebsd.org Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) Message-ID: <199709080623.XAA10617@MindBender.serv.net> In-Reply-To: Your message of Mon, 08 Sep 97 11:48:06 %2B0930. <19970908114806.25653@lemis.com>
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Warning: In continuing this discussion, I risk going off into a
tangent. I feel this is still information relevant to people planning
on new hardware purchases. However, I think we have firmly
established the players and the facts in this matter, and if you don't
care to read more, skip this thread now.
>> I think it's more because EIDE is cheaper, and there are a helluva lot
>> of cheap EIDE drives out there. Plus, some people aren't willing to
>> spend the extra on SCSI, but still want the performance.
[...]
>> IDE has always been an exercise in compromises. EIDE has just hacked
>> on a lot of turbo-chargers and accelerators, making it much better at
>> competing with SCSI on the low end. However, even UltraIDE (or
[...]
>The annoying thing is that the price isn't that much higher. It's
>just because the volume market is (E)IDE that the prices difference is
>exaggerated.
Not entirely. Yes, there are _some_ drives where you can find
identical models in EIDE and SCSI form. And they usually end up being
slightly more expensive in SCSI form, where the largest part of the
difference may simply be due to the relative manufacturing volues.
But the majority of the SCSI market tends to be "higher-end" drives,
in completely different models.
For example, more mass-market oriented drives (read higher tolerances/
lower build quality) that spin 4500-5400 RPM at the max, making up
most of the EIDE drive market. In the SCSI market, 7200 RPM is
becoming common, and 5400 RPM is almost the bottom-line, with 10000
RPM drives now available.
What's more, EIDE's potential is commonly compared with SCSI using
EIDE hardware that exists in a laboratory, or is just starting to hit
the market, and comparing to SCSI hardware that is widely available.
For example, UltraIDE, with 33MB/s. Almost none of the motherboards
currently in existance support this mode. Yet, drives are already
being marketed this way. Compared with Ultra-Wide SCSI, at 40MB/s,
which is widely available, and has been for a few years. I'm not
blaming anyone, or saying this is an industry consiracy -- this is
just the way things have played out, and it's good to be educated on
what's going on.
My final note is that over the last four years or so, I have had more
(E)IDE drives fail (3) than SCSI drives (1) in my own systems. And I
have owned more SCSI drives (11) than (E)IDE drives (5). Holding the
drives in my hand, I can tell the difference in build quality. My
experience is that there truly is a difference in the quality of
components that go into each kind of drive.
So, to end my little dissertation, I just want to say that I _don't_
think EIDE drives are "evil". I don't think this has to be a
religeous issue. Which is also to minimize those who smugly say "Now,
who said SCSI was better?" or "Now, who said SCSI was faster?" I just
did. But if you fully understand the merits of each, and you still
think EIDE is the best use of your money, then good for you.
Personally, I only put EIDE drives in my Win95/DOS/Game machine,
because SCSI just wouldn't give me any advantage there. But my NT box
is entirely SCSI driven, just as my NetBSD box is. I don't currently
have a FreeBSD box running, but when I did, it was also SCSI.
One final ironic note of interest: for some time, I had one EIDE drive
in my NetBSD system, which was used as an emergency backup boot, in
case something on my main SCSI setup got toasted, or some other
catastrophy. I have five SCSI drives in that system, three of which
are older than the EIDE drive. The SCSI drives get used for all
system activity, so are tickled constantly by cron, daily scripts,
email, software builds, etc., with several minutes of non-stop load at
least once per day. The EIDE drive just sat there, only having to
receive a tarball once each day, and rotate old backup tarballs. I
just had to send the EIDE drive back for repair/replacement because it
developed a severe mechanical failure. All the SCSI drives are still
running strong.
The standard qualifiers apply. This is one guys' experience, on a
single system, with a small number of drives. Your mileage and karma
may vary.
-----------------------------------------------------------------------------
Michael L. VanLoon michaelv@MindBender.serv.net
Contract software development for Windows NT, Windows 95 and Unix.
Windows NT and Unix server development in C++ and C.
--< Free your mind and your machine -- NetBSD free un*x >--
NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
NetBSD ports in progress: PICA, others...
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