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Date:      Sun, 11 Feb 2001 01:14:31 -0600
From:      Mike Meyer <mwm@mired.org>
To:        "Ted Mittelstaedt" <tedm@toybox.placo.com>
Cc:        <questions@freebsd.org>
Subject:   RE: Problems installing 4.x on large disks
Message-ID:  <14982.15319.193759.406761@guru.mired.org>
In-Reply-To: <002d01c093cb$9ba1f2e0$1401a8c0@tedm.placo.com>
References:  <14981.53225.50061.220090@guru.mired.org> <002d01c093cb$9ba1f2e0$1401a8c0@tedm.placo.com>

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Ted Mittelstaedt <tedm@toybox.placo.com> types:
> > Yup. And the last price/performance study I saw for that came down in
> > favor of a custom RAID box that had a bunch of UDMA drives in it and a
> > SCSI port to talk to the system. UDMA controllers are cheap enough you
> > can throw one in with the HDA and still beat SCSI prices.
> Yes, I've seen more of those kinds of things, as well as the IDE raid cards.
> While they aren't yet as standard as a SCSI setup who knows we may see
> them in wide use one day.

I was actually shocked to discover this. But I could buy the custom
IDE box for less than it would have cost to buy the SCSI drives and do
this in software.

> Certainly it's to the drive manufacturers advantage to kill off one
> specification
> over another so that eventually all disk drives are of a single type.

Maxtor already quite making SCSI drives. I was dissapointed, as I
remember getting good results with their SCSI drives (actually,
vendor-rebranded versions) in the past.

> Now, if you can only spend, say $500 on a new system that has IDE and for
> an extra $300 you can make it SCSI, well then you probably are going to be
> making those IDE/SCSI/RAM tradeoffs.  But if your going to be spending $1500
> on a system, in my opinion you have gotten to the point that an extra $300
> to get that measure of reliability and performance of SCSI is nothing.
> Keep going up the price scale, to say $5K, and the cost difference becomes
> negligible.

I wouldn't argue with those numbers - but these days, $1500 is more
than the average workstations costs.

> But, if I was only given $500 to put together a low-cost server, I wouldn't
> go out and buy brand new hardware with IDE and a cheap motherboard and box.
> I'd buy an older server-class box from Ebay or some used equipment dealer.
> Many of them come with raid arrrays, multiple CPU slots, and a lot of other
> assorted goodies and their reliability is going to be immensely better than
> a clone box slapped together with components designed for the home user.
> I'll always trade off performance for reliability in a tight-cost situation,
> and let me point out that even an older Pentium Pro 200 with a RAID array
> of slower disk drives is perfectly able to totally saturate
> Ethernet if your just using it as a fileserver.  There's a point in server
> work where more performance on the server doesen't buy you anything,
> depending, of course, on what your doing on the server.

If I were going to build a fileserver, I'd do it that way as well. And
the point that "more performance doesn't buy you anything" is an
argument *against* SCSI, not more it. You spend more on SCSI to get
better performance.

> > Again, if you don't believe my numbers, run your own tests and tell us
> > about it.
> There's that saying about lies, damn lies, and benchmarks.  If your seeing
> better
> performance from a 10MB IDE disk than a 10MB SCSI disk, for that statement
> to
> have any validity you really need to post your setup with model numbers,
> adapter cards and all that.  Do I believe that you saw that difference?
> Yes,
> because it's certainly possible to put a SCSI disk with a slower seek time
> against an IDE disk and get better numbers from the IDE.  It also depends
> a lot on the test too, what kind of data was being written back and forth
> and
> all that.

Just the opposite in this case. The SCSI drive was a Seagate Barracude
9LP on a 7890, 7200 PRM with a 7.4ms seek time. The IDE drive was a
Maxtor DiamondMax plus, 7200rpm with a 9ms seek time. The test
software was bonnie.

> I'm a SCSI bigot because in all the servers I've worked on,
> I can count the number of failures on SCSI disks that wern't full-height on
> the fingers of one hand.  I've lost count of the IDE disks I've sent back
> for
> replacement.  In all the workstations I've worked on, the SCSI ones
> were always faster than IDE.  And I've never had as many incompatability
> problems with SCSI systems as with IDE.  Now, maybe I need to come into the
> 21st
> century, but I'll always choose SCSI over IDE if I have a choice.

I haven't *ever* had an IDE drive fail. Then again, I didn't buy PC
hardware until slightly more than two years ago (because doing
performance tests against RISC hardware showed that the
price/performance for PC hardware blew the RISC hardware away), and
didn't start using IDE drives until about 18 months ago, after I did
the tests above. The only IDE drives I've seen die were old ones (~600
meg sizes) that came showed up with second-hand hardware. On the other
hand, I've lost track of the number of SCSI disk drives I've seen
fail, in both full and half-height sizes.

I admit that if I were going to build a system for that needed 7x24
reliability and was mission critical, I wouldn't be buying IDE
drives. I wouldn't buying PC hardware, either. My experience is that
it's not as reliable, and you can't properly manage it over a serial
line (well, not without unusual hardware).

	<mike
--
Mike Meyer <mwm@mired.org>			http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.


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