Failover is a mechanism in systems engineering and IT infrastructure that ensures high availability and reliability by automatically switching to a standby system, server, or network in the event of a failure in the primary system. This process helps maintain continuous operations, minimize downtime, and reduce the impact of outages on critical systems and services.

Failover can be applied to various components of an IT system, such as databases, servers, network connections, and storage systems. In environments where uptime is critical, such as financial services, healthcare, or e-commerce platforms, failover mechanisms ensure that disruptions are minimal, and services continue to run without significant interruption.

There are two main types of failover setups: active/passive and active/active. In an active/passive failover configuration, the primary system handles all tasks, while a secondary (passive) system remains idle but ready to take over in case the primary fails. The passive system monitors the health of the primary one, and when a failure occurs, the passive system activates and assumes the responsibilities of the primary system. This setup ensures continuity but may involve a brief downtime during the switchover.

In an active/active configuration, both systems are fully operational and share the workload. If one system fails, the other continues to handle requests without any interruption, making the switchover seamless and avoiding downtime altogether. Active/active failover setups are more complex and expensive to maintain but are often used in mission-critical environments where even the slightest disruption is unacceptable.

Failover mechanisms are commonly paired with load balancers that distribute traffic across multiple systems to avoid overloading any single one. For example, cloud service providers like AWS, Google Cloud, and Microsoft Azure offer automated failover as part of their high-availability and fault-tolerance solutions.

In summary, failover is an essential strategy for ensuring system reliability and minimizing service disruption during unexpected outages. Whether using active/passive or active/active configurations, failover systems provide the resiliency needed to keep critical operations running smoothly, even when components fail.