Eric Andersen wrote:
I find Erik Trimble's statements regarding a 1 TB limit on drives to be a very
bold statement. I don't have the knowledge or the inclination to argue the
point, but I am betting that we will continue to see advances in storage
technology on par with what we have seen in the past. If we still are capped
out at 2TB as the limit for a physical device in 2 years, I solemnly pledge now
that I will drink a six-pack of beer in his name. Again, I emphasize that this
assumption is not based on any sort of knowledge other than past experience
with the ever growing storage capacity of physical disks.
Why thank you for recognizing my bold, God-like predictive powers. It
comes from my obviously self-descriptive name, which means
"Powerful/Eternal Ruler" <wink>
Ahem.
I'm not saying that hard drive manufacturers have (quite yet) hit their
ability to increase storage densities - indeed, I do expect to see 4TB
drives some time in the next couple of years.
What I am saying is that it doesn't matter if areal densities continue
to increase - we're at the point now with 1TB drives where the number of
predictable hard error rates is just below the level which we can
tolerate. That is, error rates (errors per X bits read/written) have
dropped linearly over the past 3 decades, while densities are on a
rather severe geometric increase, and data transfer rate is effectively
stopped increasing at all. What this means is that while you can build
a higher-capacity disk, the time you can effectively use it is dropping
(i.e. before it experiences a non-recoverable error and has to be
replaced), and the time that it takes to copy off all the data from
drive to another one is increasing. If X = (time to use ) and Y =
(time to copy off data), when X < 2*Y, you're screwed. In fact, from an
economic standpoint, when X < 100 * Y, you're pretty much screwed. And
1TB drives are about the place where they can still just pass this
test. 1.5TB drives and up aren't going to be able to pass it.
Everything I've said applies not only to 3.5" drives, but to 2.5"
drives. It's a problem with the basic winchester hard drive technology.
We just get a bit more breathing space (maybe two technology cycles,
which in the HD sector means about 3 years) with the 2.5" form factor.
But even they are doomed shortly.
I got a pack of Bud with your name on it. :-)
--
Erik Trimble
Java System Support
Mailstop: usca22-123
Phone: x17195
Santa Clara, CA
Timezone: US/Pacific (GMT-0800)
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