264 bytes = 16,777,216 terabytes
It’s actually not that much. It’s just 8½ million 2 TB disks.
Purchased at retail from Amazon.com @ $80 each, that’s $671 million, easily within the reach of governments and large corporations (a non-retail bulk purchase would be cheaper, even if you account for failed drives, adding some redundancy, and the disk manufacturers’ power-of-10 tax).
Do we need to think about 128 bit byte addresses for disks yet?