OMG if bluray level storage was around in the early 90s imagine what today would be like.
If you think Blu-Ray is good, look at what Sony has in "Archival Disc" and is LITERALLY holding back from the consumers right now.
ODA (Optical Disc Archive) Gen 3, using Archival Disc branded Optical Discs, provide 5.5 TB of storage per cartridge with 500 GB per Optical Disc.
Each Archival Disc is Double Sided & Triple Layered.
At 500 GB, that's 83.3… GB per Layer.
Remember, Blu-Ray was Quad Layered, and Sony/Panasonic is literally holding back on what can be designed into a MiniDisc like Cartridge for home Archiving purposes.
Imagine what a large MiniDisc like shell over a standard 120mm Archival Disc used for Double Sided storage / Reading / Writing with Quad Layers could do.
That would be 666.6… GB per Disc using Double-Sided Quad Layered disc using Archival Disc Gen 3.
Once Sony/Panasonic hit Gen 4, that could double to 1333.3… GB per Disc.
Finally, slightly past the 1 TiB per Disc mark at 1.302 TiB per Disc using Double-Sided Quad Layered.
If Sony/Panasonic wanted to increase the density by adding layers to the middle of the Optical Disc, similar to HD-DVD instead of mounting them to the outside, you could see another doubling of density with minimal impact on manufacturing costs.
By making Double-Sided Optical Discs, Archival Discs have to be sandwiched from two pieces with a reflective core anyways, adding in a data layer at the center would be relatively trivial for mass production, with minimal complications since you have to do that with the making of DVD's and Double Sided discs. Combining the two techniques could create Double-Sided 8x layer per side discs in practical theory with 16x layers in total.
It wouldn't be the first time in history that there have been multiple data layers spread that far apart.
SACD did that with a CD & DVD layer in one disc.