What is Server Redundancy?
In terms of fault tolerance, server redundancy refers to the practice of having a secondary computer system or network device that will take over when the primary server fails. Systems that use server redundancy are able to reduce or eliminate any network downtime.
Using a process known as server failover, when a failure or interruption is detected, the operations of the primary server will be transferred to the secondary device. This transition can be designed to happen transparently and without the need for any human interaction.
Some purposes for server redundancy include:
- Maintenance - If one server requires maintenance, it can be taken offline while the secondary or redundant server runs the system operations.
- Fault Protection - In the case of disaster, having a network of clusters or servers can help ensure that your system remains available.
- Load Balancing - Servers that handle heavy traffic may employ the services of secondary redundant servers to help balance the load.
It is important to note that not every system that implements multiple servers experiences this type of fault tolerance and high availability. Server redundancy can also simply refer to a system that utilizes more than one server for the purposes of handling greater loads and reducing stress.
For a system to benefit from high availability, it must be both redundant and be able to apply a failover procedure. In this way, when a planned or unplanned interruption does occur, server failover will direct the operations of the primary server to the secondary server. This transition can occur instantaneously (within milliseconds) and prevent any interruptions in service.