You can provide geographical redundancy by clustering application servers over WAN. Also called disaster recovery, this configuration protects you in the event of disruption of service at a location due to a network, power outage, or a natural disaster. In the following illustration, the company has a redundant telephony system and redundant application servers. The degree and kind of survivability depends on how much system capacity is used. If Location Atlanta is running at or near 200 port capacity and a hurricane strikes the location, the Location Atlanta DR site takes over without loss of service. If Location Atlanta is using only 100 ports, Location Atlanta can survive a complete network or power outage at the main location and a failure of one of the application servers at the DR location.
