Wait till memresistors get here. That will basically eliminate the distinction between ram and disk.

https://en.wikipedia.org/wiki/Memristor#1808

"They can potentially be fashioned into non-volatile solid-state memory, which would allow greater data density than hard drives with access times similar to DRAM, replacing both components.[14] HP prototyped a crossbar latch memory that can fit 100 gigabits in a square centimeter,[8] and proposed a scalable 3D design (consisting of up to 1000 layers or 1 petabit per cm3).[66] "