These two words are commonly used to describe high availability infrastructure and server architectures, but it is nonetheless easy to get confused when trying to understand what they really mean.

What is Resilience ?

“Resilience” is often used to describe a network with an “active – active” setup. A good example is how we use multiple network links to different locations: each link always has available capacity to handle failures in another link. During a failure situation, traffic will be routed over the working link, but the end-user will not experience any difference on service availability.

What is Redundancy ?

“Redundancy” means that you have an extra unit of something which can be put into use when necessary. With a redundant PSU, the server uses only one PSU at a time, but if the primary PSU fails, the secondary PSU will be ready to take over.