Computers can be taken offline for preventive maintenance without disturbing cluster operations. WLBS combines two or more Windows NT servers into a single virtual server, called a cluster. Each server runs a copy of the server application, such as a worldwide web server, and WLBS distributes the networking workload among them. This speeds up normal processing so that Internet clients see faster turnaround on their requests. If one server should fail or go offline, WLBS automatically detects the problem and redirects network traffic to the remaining servers, thereby ensuring that service is not interrupted while at least one server is available.
Recovery requires no more than ten seconds.
However, a second network card is not required if the clustered servers do not need to communicate with each other. Each server runs a separate copy of the desired server applications, such as web servers, FTP, telnet, e-mail, etc. For some services, such as web servers, a copy of the application runs on all servers within the cluster, and WLBS load balances the workload between them. For other services, such as e-mail, only one copy of the service may run within the cluster. Instead of load balancing these services, WLBS allows the network traffic to flow to one server, and it moves the traffic to another server in case of failure.