How to make a 3-tier app on a single server that would be easy to distribute to multiple machines

I am curious about what would be the best way t开发者_如何学Goo create a 3-tier application that is supposed to work on separate servers on the same cluster, that works on the same server.

Would using REST to connect representation tier to logic tier, as well as connect to DB both running on localhost? Are there any frameworks for this?

You can check Kohana framework to do this. It has an excellent request execution mechanism where you can make external requests from inside your application.