# Introduction to Failover System
A failover system is a set of established clustering technologies designed to provide redundant implementations of IT resources in order to increase their availability and reliability. In the event of an active IT resource becoming unavailable, a failover system is set up to automatically transition to a standby or redundant instance of that resource.
# Applications of Failover System
Failover systems are typically used for mission-critical software or reusable services that could create a single point of failure for several applications. Such systems may involve the replication of IT resource instances across multiple geographical locations in order to provide redundant implementations that are monitored for any defects or unavailability conditions.
# Benefits of Failover System
The main benefit of a failover system is its ability to provide higher levels of availability and reliability for IT resources. By having redundant implementations of IT resources, organizations can ensure that their mission-critical applications and services remain operational even if one instance becomes unavailable. This can help to avoid costly downtime and ensure that businesses are able to continue operations without any disruption.
Configurations of Failover Systems
Active-Active Failover System
An active-active failover system is a redundant IT resource setup where two or more implementations actively and synchronously support the workload. Whenever a fault is detected, the processing is transferred to the IT resource that is still functioning. To prevent overloads, a load balancing scheduler is used to evenly distribute the workload among the active instances. When a failure is detected, the failed instance is removed from the scheduler.
Active-Passive Failover System
An active-passive failover system relies on a standby or inactive implementation to take over processing from an IT resource that becomes unavailable. The associated workload is then directed to the instance taking over the operation. To ensure that the workload is redirected to the correct instance, specialized load balancers are used to identify failure conditions and eliminate failed IT resources from the distribution. For IT resources that require execution state management, redundant or standby IT resource implementations must be able to share their state and execution context.