The traditional term of redundancy is to create an architecture called No Single Point of Failure(NSPoF). The availability of the system is guaranteed by the fact that there is no single breakdown which can cause a service unavailability. Thus, a redundancy system to support a simultaneous breakdown of the N component does not work at N+1. Therefore, this system cannot be defined as highly available as there is a subtle or permanent service unavailability.

The objective of defining a highly available information system is to allow users to work beyond the usual usage frequency of the information system. It is essential to define preventive and protection measures to limit the downtime and to implement rapid methods of restoration.