Working with Portal Server Building Modules
As stated earlier, a building module consists of a a Portal Server instance, a Directory Server master replica for profile reads and a search engine database. As such, at least two building modules are necessary to achieve NSPOF, thereby providing a backup if one of the building modules fails. These building modules consist of four CPUs by eight GB RAM.
When the load balancer detects Portal Server failures, it redirects users’ requests to a backup building module. Accuracy of failure detection varies among load balancing products. Some products are capable of checking the availability of a system by probing a service involving several functional areas of the server, such as the servlet engine, and the JVM. In particular, most vendor solutions from Resonate, Cisco, Alteon, and others enable you to create arbitrary scripts for server availability. As the load balancer is not part of the Portal Server software, you must acquire it separately from a
NOTE The Access Manager product requires that you set up load balancing to enforce sticky sessions. This means that once a session is created on a particular instance, the load balancer needs to always return to the same instance for that session. The load balancer achieves this by binding the session cookie with the instance name identification. In principle, that binding is reestablished when a failed instance is decommissioned. Sticky sessions are also recommended for performance reasons.
NOTE In general, the Directory Server instance in each building module is configured as a replica of a master directory, which runs elsewhere. However, nothing prevents you from using a master directory as part of the building module. The use of masters on dedicated nodes does not improve the availability of the solution. Use dedicated masters for performance reasons.
