On Jul 19, 2006, at 2:17 AM, Hunkeler Peter (KIUB 34) wrote:
So assuming you could use the whole drive, the number of these
current
generation drives that you would need to back a single address
space is
(2**64)/(2**38) = 2**(64-38) = 2**26 = 67,108,864
Back in my "old life" I once did a presentation at an IBM customer
meeting trying to illustrate how much 2**64 is. Besides a similar
DASD device calculation, I also did a simpified swap time calculation.
At 100MB/s sustained transfer speed, it takes 5850 years to transfer
all bytes of a single 64bit AS. Make that 10GB/s and use 100 devices
in parallel it still takes 210+ days.
According to Word, the PoP has about 4'000'000 characters and is
roughly 5cm thick. So 4 of them fit into one 16MB AS and this
corresponds to a pile of paper of 20cm height.
Going to 31bit multiplies these figures by 128: 512 PoPs and
25.6 meters. Going to 64bit from 31bit multiplies them by another
8 billions: 4400 billion PoPs and you can travel all the way from
the Earth to the sun and half this distance further on on that
"bridge of PoPs"..... have good journey :-)
History has shown all these "this will sufficce forever" statements
have provben that "forever" is a relatively short period of time. So,
I concluded my presentation stating that 64bit will do it for a
couple of years.
Peter Hunkeler
CREDIT SUISSE
Peter,
There was a GUIDE white paper given 15+ years ago that indicated
(IIRC) a petabyte was (sorry I lost the table from the presentation)
needed back then (for backups and real "online" data combined). But
the jist of it was that soon a petabyte was just not going to be
large enough.
The Largeness of the numbers just floored me back then, so I am not
impressed with 64 bits at all.
Ed
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