Some cheap and durable archival storage would be nice. Perhaps by storing data in grooves on ceramic discs. (Which is essentially what cds did). Though, preferably without high speed rotation, and reading more than one bit at a time by e.g. taking a picture of the surface through a microscope. How about 1 PB per disk?

I was wondering why we dont have something like that.

Unfortunately, it turns out that, with Blue-ray discs, we're already approaching the optics limit of what visible light (easily) gets us, and they're already cheating with multi-layer storage for the 100GB option. Thus youd need a complicated EUV or electron beam setup for smaller feature sizes.

Say i want my 1PB disk in cd format. A cd has r=6cm. Thus A~=100cm^2. A/1PB= 1.25e-18m^2= 1.25 nm^2, or about 5x5 atoms per bit :/

I guess we're better off by just scaling up flash production and stacking those elements vertically.

Edit: Turns out we need volumetric storage. By using a material that is transparent to the laser wavelength, by intersecting two precisely focussed beams, the local intensity suffices to absorb two photons at once (stops being transparent) allowing you to select a volumetric point to interact with. This allows a couple hundred of layers until refraction breaks our resolution.