The plan to switch Apple file systems from HFS+ to ZFS

I was reading about the plan to switch Apple file systems from HFS+ to ZFS and I came across this in the article about ZFS in wikipedi saying:

ZFS is a 128-bit file system, so it can store 18 billion billion (18.4 × 10¹⁸) times more data than current 64-bit systems. The limitations of ZFS are designed to be so large that they will not be encountered in practice for some time.

Ok… that’s nice. But actually how much data is that? Can you give an example? Yes, it seems it’s pretty big:

Project leader Bonwick said, “Populating 128-bit file systems would exceed the quantum limits of earth-based storage. You couldn’t fill a 128-bit storage pool without boiling the oceans.”

Ok… but how can one know that? What is the relationship between just saying stuff and spelling it out mathematically? Well, it seems physicists at least try to be realistic about the space time we live in:

Later he clarified:

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.

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 1.2×1028 J. The mass of the oceans is about 1.4×1021 kg. It takes about 4,000 J to raise the temperature of 1 kg of water by 1 degree Celsius, 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 2.4×106 J/kg * 1.4×1021 kg = 3.4×1027 J. Thus, fully populating a 128-bit storage pool would, literally, require more energy than boiling the oceans.

Ah, yes… I knew it wasn’t that big.