Once the main advantages of having hypervisors is that you can have strongly isolated services within a single machine. But it's really hard to actually build these specialised services; that is, until MirageOS came along. This post discusses how to build so-called "stub domains" for Xen using MirageOS.
Breaking up is easy (with OPAM)
Build isolated services with ease using MirageOS and OPAM on Xen hypervisors.