Run From Solid State Store On Mech Drive?

I am going to build a system (actually many of them) I would like to have two drives in this system. one a very fast reasonably large (100 gig) plus VERY fast solid state hard drive and the other a very fast and very large (10 or 2 Teri) mechanical drive. My question is how do I setup the prefetch or cache or whatever to run the operating system and my recent history of programs off of the solid state and have the mechanical drive there with everything on it in case I choose to something new into the recent history list by running some program once. also have oldest bumped off solid state, when space becomes an issue, but still keep it on mechanical hard drive. I think that this system will appear to run faster except the first time you run a program. I think this would be useful for instance on a system that plays the same online game everyday. Or works with the same complicated drawing in auto-cad for weeks. I have my own ideas about how to do this, but I thought I might throw this out there to what it sounds like when it hits the wall.