You've probably noticed a third block in the figure, called a Web garden. When we introduced the term "worker process" earlier in this section, the explanation indicated that a single worker process forms an application pool to which Web applications and sites are assigned, but that is not always the case. When constructing an application pool, the administrator has the option to decide how many worker processes to assign to the pool. When two or more worker processes are configured as part of an application pool they form what is referred to as a Web garden. A Web garden allows an application to achieve higher scalability, since multiple processes are used to process requests on its behalf. A Web garden is like a Web farm (in that it aims to achieve higher scalability), but within the confines of a single server.
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