In article ,
flux wrote:
In article 1112979104.459192@smirk,
wrote:

say: desktop class drives are very cheap, have very high capacity, but
they are slow, and unreliable (both in overall livetime, and also in

Cheap yes, high capacity yes.
Slow no, unreliable no.

Buy one of each, open them up. In the ES (Enterprise) drive, you'll
find small platters (about 1.5 to 2 inches), spinning at 10K (are
those still available commercially?) or mostly 15K RPM. In the DT
(desktop) drive, you'll find large platters, spinning at 7200 or fewer
RPM. Then look at the actuator magnets. The ones in the ES drive are
much larger, meaning the actuator can move much faster. Then look at
how the platter cavity is sealed against outside air: ES drives are
near perfectly sealed against dust. Then count the air filters: ES
drive have way more.

Now buy a few more drives, and put a few oscilloscopes on them, and
watch what happens while they run. For example, put a scope on the
servo signals (real professionals do this in software of the servo
processor, amateurs have to scope the actuator drive signals), and
watch how accurately the drive is servoing. Now start vibrating the
drive (simulating the effect of the cooling fan in the computer, or
the second drive or CD-ROM next to the drive), and watch how well the
servo tracks the vibration. You'll find that the DT drive is servoing
rather crudely, and can' handle vibration well (why: servo processor
much less powerful). Then start doing IO while watching the servo.
You'll most likely find that the DT drive will actually stop servoing
while writing, with the head flying blind (why: servo processor has to
do double duty running the data path, while an ES drive has separate
hardware for that).

Look at the PC boards of the two boards, and count the chips. Measure
the Flash-ROM capacity of each drive (gives a crude indication of the
complexity of the firmware of each drive, that is the software
development cost that went into the drive). Get the wholesale price
of all the chips (you'll have to estimate the ASICs by measuring die
area). You'll find a significant difference here.

Replace the scope on the actuator with a storage scope, and measure
how long the actuator really needs to settle on a track after a move
(you can also do this in software, but that's actually tricky
business). You'll find that ES actuators move about twice as fast
(and suck way more power than DT drives while doing that, there is no
free lunch). Actually: drives generally use much more power when busy
(writing and in particular seeking), so take a bandsaw to a few
drives, and measure how thick the aluminum and copper structures that
conduct heat away to the frame are; after all, you want to keep the
drive cool (heat is the enemy of just about everything in the world).
If you want to be neat about it, open the drive, and put a dozen
thermocouples in strategic locations, button it back up, and run it
for a while.

Now throw a nasty workload at the drive, with a few dozen outstanding
IOs at the same time (classic ATA drives can't do that at all, modern
ATA drives can do it in principle, but because that capability is not
used by Windows device drivers, it is implemented in a haphazard
fashion). Watch the order in which the drive actually executes the
IOs, and how many IOs it can queue. You'll find that under overload
conditions, the ES drive acquits itself fairly well, using a pretty
sane queue management algorithm. On the DT drive, it's anyones guess.

Doing these tests will require a well-equipped lab, a few dozen
drives, and a few weeks of time (if you are good at this kind of
stuff). Or friends in the business that have done these tests, and in
some cases published them (I pointed to the Dykes/Anderson/Riedel
paper in a previous post).

drives being sold with SATA interfaces. Unfortunately, I haved talked
to experts in the field (names withheld), which have performed a
teardown analysis on some (but not all!) of these ATA/SATA

Let's have the names.

Please ask your employer to get them through official channels. Don't
forget to sign the requisite NDA agreements, and you might have to pay
a little license fee here or there for information like this. Don't
worry, if you use a few hundred thousand drives per year, the extra
cost will not be significant.

Now, naturally you can take low-reliability drives, and using

Are there any such drives any more?

Why are most ES drives sold with 3- and 5-year warranties, and DT
drives with much shorter warranties (1 year at many manufacturers)?
Coincidence?

I'm not sure I believe you.

Too bad. No skin off my avocado.

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Ralph Becker-Szendy