We are huge fans of OpenVZ container level virtualisation. Although we're quite puzzled as to why it is not more popular.
What is OpenVZ you ask?
OpenVZ is operating system-level virtualization based on a modified Linux kernel that allows a physical server to run multiple isolated instances known as containers, virtual private servers (VPS), or virtual environments (VE). The preferred term these days is container. Containers are sometimes compared to chroot or jail type environments but containers are really much better in terms of isolation, security, functionality, and resource management.
Why we use OpenVZ
In a nutshell: Because a ...