Infrastructure Patterns
The next set of patterns in this cluster focuses on the physical infrastructure. The context for these patterns is an infrastructure that supports an application distributed over more than one server. Specifically, these patterns do not address mainframe or other large multiprocessor infrastructure configurations.
Tiered Distribution organizes the system infrastructure into a set of physical tiers to provide specific server environments optimized for specific operational requirements and system resource usage. A single-tiered infrastructure is not very flexible; the servers must be generically configured and designed around the strictest of operational requirements and must support the peak usage of the largest consumers of system resources. Multiple tiers, on the other hand, enable multiple environments. You can optimize each environment for a specific set of operational requirements and system resource usage. You can then deploy components onto the tier that most closely matches their resource needs and enables them to best meet their operational requirements. The more tiers you use, the more deployment options you will have for each component.
Three-Tiered Distribution refines Tiered Distribution to provide specific guidance on structuring the infrastructure for Web applications with basic security and other operational requirements. The pattern suggests that the solution's servers be organized into three tiers: client, Web application, and data. The client and data tiers are self-explanatory, and the Web application tier hosts application business components as well as the Web presentation components. For solutions with more stringent security and operational requirements, you may want to consider moving the Web functionality into its own tier.
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