HA Roles, Synchronization and Failover

The primary node and secondary node send heartbeats to each other to detect if its peers are alive. If the primary node is not accessible, such as during a reboot, a failover occurs. You can also configure a ping server to regularly check the unit's network condition and downgrade itself to secondary type to trigger a failover. In a failover, the secondary and primary switch roles and the cluster IP addresses change, as indicated by the boxes in the lower image.

In a cluster, there is only one copy of a job, which is in the unit that the primary assigned it to. Jobs that are assigned to the "old" primary will not be scanned in another cluster unit after failover.