DNA also sounds interesting, though it doesnt seem like a good way of preserving data long term. DNA is very fragile, and seems like an odd route to take for long term archiving.
Yeah the 5D quartz disk is very cool.
Anyways if you think about storage density DNA isn't that "odd". With DNA you can store dozens of copies of the data and parity checks in a very small space so even if some gets corrupted you can still get it. I get that organic stuff has its limits but the density is just mind blowing.