What is racetrack memory? It is basically a series of magnetic areas, corresponding to bits, strung along a wire (carbon nanotubes are great). It is faster than flash memory, but much slower than ram. It has the potential to store a huge amount of data in a very small amount of 2D space, since the wires can be crammed close together and will drop down into the third dimension. IBM is working on this and has made some great recent developments (this year).