[Novalug] Hard Drives -- capacity, number of platters and reliability

[Bryan J. Smith]

Dual and, even more so, single platter drives can have extremely high reliability.
It's not always a bad thing to stay with a lower capacity in a new model.

The current, leading, commodity platter capacity is 500GB in 3.5" (possibly
even 667GB now -- haven't checked if the latest 2TB disks are 3 platter) and
333GB in 2.5" since mid-'09.

So if you can verify a 500GB 3.5" drive or 320GB 2.5" drive is a single platter,
late model drive, you should find its longevity is much better than an increased
capacity unit of the same series.

I know one of Seagate's most reliable drives was the Barracuda 7200.7 (note
the "7") series.  It was a 100GB/platter disk available only in a 200GB (dual
platter) offering.  I had dozens with no failures whatsoever.

The industry standard is only to put a maximum of four (4) platters in 3.5x1"
and two (2) platters in 2.5"x9.5mm.  It's been a long time since any vendor
has done a 3.5xHH, although you will find 2.5"x12mm disks with three (3)
platters in some cases.

The only vendor I've seen violate these industry standards is IBM now Hitachi,
with five (5) platters in 3.5x1" and three (3) platters in 3.5"x9.5mm.  They are
rare but should be noted.

There is at least one vendor (Seagate) that does 2.5"x1" (25.4mm) with over
a half-dozen platters by putting it in a 3.5x1" enclosure for legacy customers who still
have 3.5" bays expecting 10-15Krpm.  All 10-15Krpm drives have been 2.5"
for the past half-decade (and every 15Krpm drive has always been sub-3"
platter).

Drives of 10-15Krpm have lower densities than drives of 5400-7200rpm drives.
I believe the top capacity of 2.5" at 10-15Krpms is only 200GB currently, for
a flagship 600GB in 2.5"x12mm.

FYI, notebooks are typically only 2.5"x9.5mm height capable (excluding those
that only take 1.8" drives, of course ;).




----- Original Message ----
From: Nick Danger <nick at hackermonkey.com>

On a good note, the quality of whats left seems to not be bad. I was 
afraid I'd start getting NOS with a higher failure rate but that hasn't 
been the case. Even with the smallish (80G-100G) drives I am buying.