Yeah, it’s a theoretical limit. You don’t need to boil any ocean to use ZFS.
Reference: >>>
If 64 bits isn't enough, the next logical step is 128 bits.
That's enough to survive Moore's Law until I'm dead, and after that,
it's not my problem. But it does raise the question: what are the
theoretical limits to storage capacity?
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, 1047-1054
(2000)]. A fully-populated 128-bit 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.
That's a lot of gear.
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 128-bit
storage pool would, literally, require more energy than boiling
the oceans.