If the original VM in the production site becomes unavailable, you can quickly restore services by failing over to its replica. When you perform failover, the VM replica takes the role of the original VM. All processes shift from the original VM on the production host to the VM replica on the secondary host. You can fail over to the latest state of a replica or to any of its restore points.
When you fail over to the VM replica, Veeam Backup & Replication changes the replica state from Normal to Failover.
Failover is an intermediate step that needs to be finalized. Depending on a disaster recovery scenario, you can do one of the following:
- Undo failover
When you undo failover, you switch back to the original VM and discard all changes made to the VM replica while it was running. The state of the VM replica gets back to Normal. You can use the undo failover scenario if you have failed over to the VM replica for testing and troubleshooting purposes and you do not need the changes made to the VM replica.
- Perform failback
When you perform failback, you switch back to the original VM and transfer all changes that took place while the VM replica was running to the original VM. If the source host is not available, you can restore the original VM to a new location and switch back to it.
When you perform failback, changes are only transferred but not published. You must test whether the original VM works with these changes. Depending on the test results, you can do the following:
- Commit failback. When you commit failback, you confirm that the original VM works as expected and you want to get back to it. The state of the VM replica gets back to Normal.
- Undo failback. If the original VM is not working as expected, you can undo failback and get back to the VM replica. In this case, the state of the VM replica returns to Failover.
- Perform permanent failover
When you perform failover, you permanently switch from the original VM to a VM replica and use this replica as the original VM. This scenario is acceptable if the original VM and VM replica are located in the same site and are nearly equal in terms of resources.
Veeam Backup & Replication supports failover and failback operations for several VMs simultaneously. In case one or several hosts fail, you can use batch processing to restore operations with minimum downtime.