This document explains use of range of off-the-shelf technologies to enhance the availability and reliability of IT infrastructure in existing installations without necessarily needing to install new hardware or make major changes to your current infrastructure.

It talks about availability as a concept, how to define it, how to measure it, and then compares notions of high availability and fault tolerance. There is a notion of carrier grade technology and carrier grade operating systems that comes from telecommunications. It explains how they can be applied to enterprise infrastructure. It also talks about virtualization, and how virtualization impacts system availability. Finally, it weaves all of these concepts together combining fault tolerance and virtualization for the best performance, price performance, and availability in existing infrastructure equipment.