One form of computer storage involves crystals, and if you send the right combination of electricity and light beams, you can create crystalline structures and store data. They are ridiculously dense in storage (if done correctly), and are pretty reliable, as they are just crystals. A downside is that it takes very precise inputs in order to store data at this ridiculous density, or extreme mental resources on [[Zoraners]]. These crystals can be found in the home universe, but are abundant in Hammer.
The density of the crystal in storage terms is decided by the size of the crystalline structures; smaller is more dense.