Scalability

Scalability is a system’s ability to accommodate a growing user population, without performance degradation, by the addition of processing resources. The two general means of scaling a system are vertical and horizontal scaling. The subject of this section is the application of scaling techniques for the Portal Server.

Benefits of scalable systems include:

• Improved response time

• Fault tolerance

• Manageability

• Expendability

• Simplified application development

• Building modules

Vertical Scaling

In vertical scaling, CPUs, memory, multiple instances of Portal Server, or other resources are added to one machine. This enables more process instances to run simultaneously. In Portal Server, you want to make use of this by planning and sizing to the number of CPUs you need.

Horizontal Scaling

In horizontal scaling, machines are added. This also enables multiple simultaneous processing and a distributed work load. In Portal Server, you make use of horizontal scaling because you can run the Portal Server, Directory Server and Access Manager on different nodes. Horizontal scaling can also make use of vertical scaling, by adding more CPUs, for example.

Additionally, you can scale a Portal Server installation horizontally by installing server component instances on multiple machines. Each installed server component instance executes an HTTP process, which listens on a TCP/IP port whose number is determined at installation time. Gateway components use a round-robin algorithm to assign new session requests to server instances. While a session is established, an HTTP cookie, stored on the client, indicates the session server. All subsequent requests go to that server.

The section Designing for Localization, discusses an approach to a specific type of configuration that provides optimum performance and horizontal scalability.