ISA Duo Automatic/Manual Failover and Failback Feature

ISA Duo™ clusterering software allows two computers running Windows NT or Windows 2000 Server to share TCP/UDP traffic loads by simply managing them as if it were a single system. By combining the resources of two computers into a single cluster network, ISA Duo™'s failover and failback feature can keep up with the demand and performance of the servers.

The main purpose of the automatic failover feature is when a server is down or fails to run, the other server will automatically take over greatly minimizing the downtime. If the primary server fails creating a failover, the secondary will take over, vice versa.. 

The client reconnection is practically transparent and they will almost have no idea their was ever a problem with the server. In either case, the client will only see the IP address of the primary server which is exactly the same IP address known to them from the start.

Once the failed server is restored, the service or application the client is using will automatically rebalance the workload in the cluster. This automatic return to your original state before the server failed is called a failback.

If administrators need to perform manual maintenance, there will only be a momentarily pause in the service. The service will then be directed to the server that is still up. The workload can easily be transferred from one server to another without causing a disturbance for clients accessing it.