In Display Server HA deployments, the primary and backup Display Server do not connect to each other. The rtvdisplay servlet is configured to connect to the primary Display Server first and if that connection fails, the servlet tries to connect to the backup Display Server. Likewise, when the backup Display Server connection fails, the servlet tries to connect to the primary Display Server.
If the DisplayServerConnectionFailback property is set to true, the rtvdisplay servlet reconnects to the primary server when it comes back on line. If set to false, it does not reconnect to the primary server unless the backup server becomes unavailable.
The Display Server is a client of the CentralServer and connects to it via fault tolerant URL (socket). This means that the data servers and historians can fail over separately or together.