Startup Process

When a pair of fault-tolerance appliances start up, the procedure described here takes place concurrently on each appliance.

Procedure

  1. When the EMS server instance starts, it waits for its peer before proceeding with the startup sequence.
  2. After contact occurs, the two EMS server instances check the state of their stores to determine which server has the most recent copy of the store data.
  3. The EMS server that has the latest store data proceeds to the active state and begins servicing clients. The other server proceeds to the standby state.
  4. The active and standby EMS servers synchronize data, such as store and configuration files, to ensure that both sides match. Synchronization is complete when both servers have the same records in their store files.
  5. The active and the standby servers begin replicating data. Replication is the process whereby the active EMS server instance writes persistent data to both its own and the standby server store files.

Result

If only one appliance in a fault tolerant pair is available, you can force the EMS server instance(s) on the available appliance to start in standalone mode. Starting an EMS server instance in a standalone mode requires an explicit command from the administrator using the forcestart command on the CLI. Neither appliance will automatically start servicing messaging operations in the absence of the other.
Note: When the second appliance is started, it synchronizes with the appliance that was forced to start. You should never force both appliances to start separately because they cannot properly synchronize their stores afterwards.