How Load Balancing Works

DeFrame load balancing is performed by the Watchdog service (Novell Dewatch Balancing Service), a Windows service that you must run on each terminal server that will participate in load balancing. The Watchdog service performs two main tasks:

• It calculates the current workload of the terminal server. The calculation is based on the utilization of the server's resources (memory, CPU usage, and so forth) and the weight, or importance, assigned to each resource. You can adjust the resource weights on a per-server basis to account for different performance capabilities (see Adjusting the Load Calculation Weights ).
• If it is designated as the primary Watchdog service for an application, it collects the workload statistics for each terminal server hosting the application and creates a preferred server list. The preferred server list is prioritized with the least-utilized server having the highest priority and the most-utilized server having the lowest priority. The application will be launched from the least-utilized server, if it is available.

You can have one Watchdog service designated as the primary service for all applications, in which case it will determine the preferred servers for all of the applications. Or you can designate multiple primary Watchdog services, each with responsibility to monitor a different group of applications.

The number of applications you assign to a primary Watchdog service depends on several factors, including the workload that the Watchdog service's server can handle and the speed of the Watchdog service's access to Novell eDirectory^TM.

Each primary Watchdog service can also have a backup Watchdog service. The backup Watchdog service can be any other Watchdog service, including primary or backup services for other applications. The backup Watchdog service becomes the primary Watchdog service only if the primary service becomes unavailable. At that point, the two services switch roles and remain that way until the new primary service becomes unavailable or you manually switch them using ConsoleOne^®.

For instructions on designating a Watchdog service as the primary service or backup service for an application, see Assigning Applications to a Watchdog Service