Failover Process
When a fault tolerant appliance loses contact with its peer, both the active and standby EMS server instances enter their paused states for a short time while the appliance determines the correct action.
The response of the appliance depends on the type of failure experienced:
- System or Power Failure
If the peer appliance is down, the remaining appliance's active EMS server instance enters the active-standalone state and continues to service clients. The standby EMS server instance also enters the active-standalone state, and begins servicing clients.
- Hardware Component Failure
If both appliances are still running but one appliance has a hardware fault, the faulted appliance shuts down its active EMS server instance. Both server instances on the functional appliance begin servicing clients in the active-standalone state.
- Connection Failure
If the fiber optic cable connections between the appliances fail, preventing the EMS server instances from communicating, the appliances continue their active server instance in the standalone state and prevent their standby server instance from being able to activate.
- Network Interface Failure
If an appliance has a network interface failure that prevents its EMS server instances from servicing clients (even though the EMS server instances can communicate with their peers on the other appliance), the appliances react in the same way as they would to a hardware failure.