The second objective talks about the logical design. When we talk about the logical design at this point in the project phase we are talking about a lower level design, compared to the conceptual design. If you take a network diagram for example, this is usually also a logical design but it contains much more information. Information you do not have at this point. So the purpose of a logical design is to dig deeper into the conceptual design and evaluate the design without getting lost in explicit connection or configuration details.
It is often not easy to understand the difference between physical, logical and conceptual design. To understand the difference, always remember the timeline. First you create a concept, something like “The customer wants to have a protected cluster with physically separated hardware”. The conceptual design is always the part the customer wants. The second step is the logical design. This is where the designer creates his logical design to fulfill the given requirements. This design should sound like “To fit the needs we need servers, connected to switches, connected to our storage.” Does the designer care about IP addresses, hostnames or hardware vendors at this point? No!
What should be shown in the logical design? Here are a couple of questions which might be part of the logical design:
- Should the Cluster use HA and DRS?
- Is Storage DRS a valid solution?
- Does the customer need storage tiering?
- Could Site Recovery Manager fit the needs?
If you are looking at a logical design you should usually see ESX hosts, physical switches, virtual switches, storages and the depencies between all components. Another hint: If the logical design is reusable at another customer without modification, it is a valid logical design.
A new part in this objective and derived from ITIL is the service catalog. A service catalog is a list of services that a company provides to its customers. The catalog should provide the following information:
- Service name (Extended Support)
- Service description (Maintenance and support of servers and components)
- Services included (Patch management, upgrades, incident support)
- Services not included (Non-standard changes)
- Services availability (24x7x365)
VCAP5-DCD Exam Blueprint v1.1
- Explain the common components of logical design.
- List the detailed steps that go into the makeup of a common logical design.
- Differentiate functional and non-functional requirements for the design.
Skills and Abilities
- Build non-functional requirements into a specific logical design.
- Translate given business requirements and the current state of a customer environment into a logical design.
- Create a Service Catalog