VCAP-DCD Objective 2.1 –Map Business Requirements to the Logical Design
February 22, 2011 
Sean Crookston 
Knowledge
- List the fundamental components of the vSphere4 environment.
- List the fundamentals of the VMware virtualization architecture.
- List the phase of logical design.
- List the detailed steps that go into the makeup of a logical design.
Skills and Abilities
- Define a logical design.
- Apply the detailed steps that go into the makeup of a logical design to a particular customer environment.
- Distinguish between a logical and physical design.
- Given a situation, translate given business requirements and the current state of a customer environment into a logical design.
Tools
- Introduction to VMware vSphere
- What’s New in VMware vSphere 4.1
- VMware vSphere Evaluator’s Guide
Objective two focuses on the logical design, where we talk about defining our infrastructure at a high level. Here we are still looking to define how we would like things laid out, but do not get into the details such as LUN sizes and other configuration items. The physical design on the other hand will contain those specific configuration items such as LUN sizes and hardware vendors/models. The below is a diagram from the Introduction to VMware vSphere guide that depicts a very basic logical design. It is important to note that logical designs typically are the basis for physical designs so there may be shades of grey as to whether a diagram is a logical or physical design.
Objective 4 will cover the Physical Design but it is important to differentiate between those two now.
The logical design phase will also likely include discussions of things like capacity and configurations, even if they aren’t necessarily depicted in your diagrams.
So what items specifically are we talking of when we talk of the logical design of a VMware vSphere 4 design? For starters we can start thinking about the environment in terms of virtual servers, clusters, and datacenters. Looking at those pieces we then may start thinking of network and storage layouts. We then may start talking about ancillary parts of the design. If we are talking about updates we may be talking Update Manager, if we are talking about management and monitoring we may be talking about vCenter. If we are talking about our DR strategy and layout we may be talking about Site Recovery Manager.
So let’s say a customer approaches us and wants a solution to their problem. They currently are partially virtualized and have a small VMware cluster of 3 servers in their main Datacenter, but would like to virtualize the rest of their servers there, the servers at their other Datacenter, and work towards a setup that is both highly available and provides disaster recovery.
So in my head right now I am thinking a DRS/HA cluster of servers at both Datacenter sites, and using SRM Replication between the two bi-directionally. The diagram below is a quick depiction of that, but probably should also include a logical representation of the storage at each site as those are the pieces that will be replicating.
During the discussion we might also find that they have a desire to separate some of their test/dev into a separate cluster but are concerned of the cost ramifications of doing so. Perhaps we know their existing three hosts are on the HCL for vSphere 4.1 and can be reused as a separate cluster?
The important point of this objective is to know the components of a vSphere environment on how to logically represent these through a proposed logical design layout. Logical designs are the basis for your physical designs so proper attention to detail here will go a long way in the overall design.
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