A dependency is a relationship among systems or services. During the discovery process, dependencies should be identified and documented. In Chapter 1, The Virtual Datacenter, we discussed the importance of taking a holistic view when designing a virtualized environment. Identifying dependencies is the key to the holistic approach of designing.
An architect must identify dependencies in order to understand what effect a design decision or change may have on other services. The architect should identify the following dependencies:
Physical infrastructure dependencies
Application and service dependencies
Dependencies can be service-to-service; for example, a web application depends on a frontend web server and a backend database. Dependencies can be service-to-infrastructure; for example, the web application requires a static IP address and a minimum of 10 MB of network bandwidth.
Physical and infrastructure dependencies are generally easier to...
