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From: Tomas Puverle (Tomas.Puverle_at_[hidden])
Date: 20060523 18:09:49
> Totally agree about more general solution.
>
> That does not change anything, but just out of curiosity some
> calculations were made: the number of atoms in the graphite of a
> pencil is < 2^72,
>
> http://www.madsci.org/posts/archives/oct98/905633072.As.r.html
>
> so the storage providing capacity to hold files with 128bit offset
> would have to contain at least as many atoms as 8*2^56 = 2^59 pencil
> leads ! Hundreds of tons of material that should be. And this is with
> just 1 atom per bit of information. Seems a bit too much for any
> conceivable technology... What FS would need to provide support for
> such capacities ?
Agreed, it would be a lot of data. However, I was mistaken about the maximum
file size. It seems that even on the very large filesystems such as ZFS and
the Veritas VxFS, the maximum size of an individual file is only 2^64.
Look here:
http://en.wikipedia.org/wiki/Comparison_of_file_systems
under the section "Limits".
With regards to your calculation, Jeff Bonwick, the designer of ZFS
filesystem made a similar calculation to yours in one of his initial blog
posts:
"Although we'd all like Moore's Law to continue forever, quantum mechanics
imposes some fundamental limits on the computation rate and information
capacity of any physical device. In particular, it has been shown that 1
kilogram of matter confined to 1 liter of space can perform at most 1051
operations per second on at most 1031 bits of information [see Seth
Lloyd, "Ultimate physical limits to computation." Nature 406, 10471054
(2000)]. A fullypopulated 128bit storage pool would contain 2128 blocks =
2137 bytes = 2140 bits; therefore the minimum mass required to hold the bits
would be (2140 bits) / (1031 bits/kg) = 136 billion kg.
To operate at the 1031 bits/kg limit, however, the entire mass of the computer
must be in the form of pure energy. By E=mc2, the rest energy of 136 billion
kg is 1.2x1028 J. The mass of the oceans is about 1.4x1021 kg. It takes about
4,000 J to raise the temperature of 1 kg of water by 1 degree Celcius, and
thus about 400,000 J to heat 1 kg of water from freezing to boiling. The
latent heat of vaporization adds another 2 million J/kg. Thus the energy
required to boil the oceans is about 2.4x106 J/kg * 1.4x1021 kg = 3.4x1027 J.
Thus, fully populating a 128bit storage pool would, literally, require more
energy than boiling the oceans."
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