| Another important aspect of building a combined WebSphere and Domino system is in the area of building high-volume, high-capacity, scalable systems. What are the design aspects of high-volume Web sites ” especially those based on both WebSphere and Lotus Collaboration tools? IBM's experience designing the Web sites for the Olympic games , which included Domino for collaboration, will serve as an example of the evolution of these Web site design concepts. Many of the design concepts for high-volume, high-availability, high profile sites that included collaboration features went through the intense proving ground of Web sites for the Olympics and other international sporting events. Both WebSphere and Lotus Collaboration tools support the concept of horizontal and vertical scaling for high-volume, high-capacity systems. These types of scaling are important for building both high availability and high capacity systems. -
Horizontal scaling consists in distributing work among many machines, some or all of which can be less powerful. Failover is a main advantage of horizontal scaling. If a machine becomes unavailable, its work can be routed to other machines containing server clones . Load balancers or IP "sprayers" can be used to distribute requests to identical multiple machines, each running an application server clone. These techniques do not have to interfere with, but can complement the workload management provided automatically by WebSphere and Domino. -
Vertical scaling consists in using the product cloning support so as to get more from each machine on which the product runs. A server and several of its clones can share the same machine, enabling you to utilize more of the machine's resources, such as CPU. This works well when the individual machines in your topology are powerful but under-utilized. IBM and other computer services companies have long hosted Web applications on the Internet for corporations as part of "outsourcing" agreements. Many of the high capacity sites are beginning to incorporate function from both WebSphere and Lotus Collaboration. Details are given in Chapter 15, "Implementing High-Volume Web Sites." |
