Analog, step two
The next step after digital recording, is three dimentional analoge. People tried this, with multi-layer harddrives, but it is still a two dimentional medium.
Imagin the needle on a record. Where ever its location, the needle reads information as verious hights. Harddrives do the same thing. Their information based on "on" or "off." Just like little kids coming up with little codes, two on and three off may mean "hello!" to a computer that reads it. This is like a vynal record in that one magnetic reader, registeres different heights at particular locations. Tape recorders work in a similar fasion. In all of these examples, information is stored at an X/Y coordinate system, and you have different results depending on the information at that particular location.
Now imagin a CD that is stacked upwards instead of just flat, so it looked like a dozen CD's ontop of one another. You would need two lasers to read it instead of one. One to mark X and Y axis, and one to mark the Z axis. You would be able to reduce the size of media by a factor of 3, while maintaning an physical analog system.
Imagin a cylindrical piece of glass. from the top looking down, it looks like a circle. And a little black tic in the glass would mean on, while blank space is marked as off. This would be just like a harddrive. However, you have a second laser reader on the side, marking at what height this tic occured. No longer do we have an on/off system like our current analog systems, but at each location, there are a million or so choices. We could store entire alphabets in the same space that we previouslly had "on/off". Now it would be "A/B/C/D/E...Z".
. If you have laser readers on top, and laser readers on the sides