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A failover (from the English failover for " failover ") is the unplanned change between two or more network services (abstracted functions that are provided by a computer network to the users or participating devices) in the event of a one-sided failure. As a result, the services can be kept highly available despite the failure of one of the systems .

In this way, business-critical applications such as databases , web servers or e-mail can continue to be made available even if a computer fails, since the second system takes over the tasks of the primary system in the event of a failure.

Both servers usually monitor each other with a heartbeat .

Since a deliberate transfer of services from one cluster node to another cannot be referred to as an error (failover), this process is also known as switchover .

Failover cluster

A failover cluster or active / passive cluster is a network of at least two computers ( cluster ) in which a second computer takes over its tasks if one computer fails.

The active system is the primary system , the waiting passive systems are the backup or standby systems .

Cluster manager software or a load balancer must be used so that failover can take place automatically and without the intervention of an administrator .

Another advantage of a failover cluster is the possibility of deliberately taking a system out of operation for maintenance purposes, whereby the redundancy is no longer given in a 2-server cluster during this period.

Individual evidence

  1. Heise: Glossary Failover. Retrieved September 7, 2018 .
  2. Techtarget definition: failover. Retrieved September 7, 2018 .
  3. Heartbeat, failover and quorum in a Windows or Linux cluster. Retrieved September 7, 2018 .
  4. Set up a failover cluster. Retrieved September 7, 2018 .
  5. Difference between failover and switchover. January 27, 2010, accessed September 7, 2018 .
  6. Failover Cluster. Retrieved September 7, 2018 .
  7. IT knowledge: failover cluster. April 10, 2017, accessed September 7, 2018 .