In computing, a failover is the process of switching to a redundant system in the event of a system-wide failure due to any number of reasons (e.g., fire, power outage, server shutdown). Many companies have a procedure in place for their systems to switch to a backup, which ensures business can continue as normal. Failover is especially important for day-to-day processing systems, such as those used by banks, production facilities, and retail stores. The backup system is usually located in another building, and may even be in another city or state.
The failover system is a mirror image of the main system, so little or no data is lost. The failover process can take several minutes to several hours, depending on the complexity of the system, and may require human intervention, depending on the design.