RAM buffers work well for large readonly workloads, but write heavy workloads will perform pretty poorly with that kind of configuration.

Mind you its all a compromise, if you know that disk IO isn't a factor for your application then servers like that are ideal. I just won't run a large database on it without something like MySQL Cluster using a Memory table. It would require 2 servers, but REALLY good performance, good reliability (just get 2 dual PSU servers in different cabinets).