This objective talks about service dependencies in your design and how to document them. Services could be everything that matters the design, DNS, databases or NTP for example. I will not go deeper into these services, instead of this I will explain the terminology.
Application Dependency Diagram
An application dependency diagram determines which entities are related with another. While discovering running services during the current state analysis you can use this information to draw down the upstream and downstream relationships. Relationships could be defined in the following terms:
- runs on / runs
- depends on / used by
- contains / contained by
- hosts / hosted by
If you have a website for example. The website runs on a webserver which runs on a linux server which is hosted by a VMware Cluster. This is an example of the dependency map:
Upstream and Downstream Relationships
Everything that happens downstream can have an effect on upstream items. For example, if the webserver crashes, the website upstream is affected and goes down. Neither the operating system, nor the cluster are affected, as this are downstream relationships. To memorize this, you could think of a house. The roof is “up” while basement is “down”. If you break down the basement, the roof upstream” also collapses.
VMware offers a product called VMware vCenter Application Discovery Manager which can assist to discover and draw down these relationships.
VCAP5-DCD Exam Blueprint v1.1
- Identify basic service dependencies for infrastructure and application services.
Skills and Abilities
- Document service relationships and dependencies (Entity Relationship Diagrams)
- Identify interfaces to existing business processes and define new business processes
- Given a scenario, identify logical components that have dependencies on certain services.
- Include service dependencies in a vSphere 5 logical design.
- Analyze services to identify upstream and downstream service dependencies.
- Having navigated logical components and their interdependencies, make decisions based upon all service relationships.