[Python-Dev] One more dict trick

[Eric S. Raymond]

M.-A. Lemburg <mal@lemburg.com>:
> > 2^64 = 18446744073709551616, which is roughly 10 ^ 22.  Let's assume
> > a memory density, of, say 2^20 machine words or roughly 8 megabytes per
> > cubic centimeter (much, *much* better than we'll be able to do for the
> > forseeable future -- remember power distribution and heat dissipation).
> 
> Where did you get those numbers from ? There are memory sticks
> with 128 MB around and these measure about 2.5 cm^2 * 1 mm.

Remember power distribution and heat dissipation.  You can't just figure 
volume of the memory ICs, you have to include power and cooling and structural
support too.  I eyeballed some DRAM modules I had lying around.

In any case, my figures aren't that sensitive to memory density.  If
I'm off by a factor of 64 the diameter of the memory sphere unly drops
by a factor of four (it's that cube-root relationship between volume
and radius).  So it's only half the radius of the Sun.  That's still
way, *way* more mass than all the planets in the Solar System put
together.

> Just you wait... someday marketing people will probably invent the
> world memory facility and start assigning a few hundred
> Terabytes for everyone on this planet to use for his/her data 
> storage -- store once, use everywhere ;-)
> 
> Let's assume we have 12e9 people on this planet by that time, then
> we'll need 12e9*100e12 = 1.2e24 bytes of central storage... or
> roughly 2^80 bytes per civilization.

Nah.  Individual storage requirements would never get that large.
Bill Joy did a study on this once and figured out that human beings
can generate about 14GB of text during their lifetimes, max.  In a
system like the Web-on-steroids one you're supposing, higher-volume
stuff like streaming video or Linux-kernel archives would be stored
*once* with URLs pointing at them from peoples' individual stores.

One terabyte (2^40) per person leaves plenty of headroom (two orders
of magnitude larger).  We could still handle a world population of
2^24 or roughly 16 billion people.  (I think the size of the Library
of Congress has been estimated at several thousand terabytes.)
-- 
		<a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a>

I don't like the idea that the police department seems bent on keeping
a pool of unarmed victims available for the predations of the criminal
class.
         -- David Mohler, 1989, on being denied a carry permit in NYC