For example, we can take a server. Server by itself is a largely redundant from a component viewpoint: multiple processors, disk drives, power supplies, cooling fans, I/O interfaces, etc. In order to prevent system failure due to the server malfunction, we increase the redundancy at the server level, in a way that connects multiple servers in a cluster system.
Despite increasingly sophisticated and reliable IT solutions, there is always a certain possibility of failure of individual system components. To avoid system downtime's due to a malfunction, during designing, we take into consideration prospective failures and also, by using redundancy method, we increase the system availability.