17 Aug 2012 by rayheffer
This week I passed the VCAP-DCD5 exam, but having already passed the VCAP-DCD4 exam I actually found it a little harder than I expected. I can’t tell you any specifics of the exam itself (other than what is on the blueprint) but I would like to share my own study method with you. You will need to be VCP5 before you can take this exam (the limited time period that excludes this pre-requisite is almost up), but even if you have done the VCAP4-DCA/DCD before, you should take a fresh approach to the DCD5. Something that helped me a lot was my ITIL experience, as I’ve previously had key involvement with Capacity and Availability management, in addition to being ITIL v3 Foundation certified . I’ll touch on this in a moment, but bear in mind that this is a Design exam and not a technical exam. Sure there are many technical areas, such as system requirements that you need to be aware of, but you need to have experience at either producing designs for your own organisation, or consultancy at delivering designs for customers. Without this knowledge, you may struggle with some of the questions around best practice, or picking the ‘best’ answer from multiple possible correct answers.
ITIL v3 touches on a number of areas that Architecting a design requires; RTO/RPO, MTBF, MTTR, are just some of the acronyms you may come across. I would focus on Capacity and Availability management (part of ITIL principles). This isn’t an ITIL exam, but some of these basic principles date back to the 17th century (http://en.wikipedia.org/wiki/PDCA), and design principles and methodologies are all based on similar ideas; Create the Vision / Strategy > Gather Requirements > Assessment > Design > Implement. In fact I’d throw ‘Validate’ in there too, no point having an implementation plan if you haven’t proved it works! The Architect
I posted an overview of the VCAP-DCD5 a while ago now, and this highlights the exam blueprint and some recommended study material, but in these notes I will provide you with a starting point for your study. Unlike the VCP5 or VCAP-DCA (lab based) exams, you need to take a more process oriented approach, think of the Architect. What does this actually mean? Rather than being all about advanced configurations, CLI commands, etc. you will need to have a solid grasp of the VMware design methodology and where that can be applied. In that sense it can be a difficult exam to study for, with more than just hard facts such as technical details, you have to focus on business requirements, and implementing technical best practices where appropriate (not just because it’s a best practice). If you are new to VMware design then I suggest that you start the official VMware vSphere 5: Design Workshop course. I’d also strongly recommend the Trainsignal: Designing VMware Infrastructure video series by Scott Lowe.
The first step is to gather the business requirements, which incidentally is the first section on the blueprint (quite rightly so too!). In real-world designs time must be spent gathering requirements as it arms you with everything needed for the design. It pays to be meticulous here, and this involves lots of questioning (Why is it like that? What do you need that for? Where are these located?), and what better way to do this than by holding workshops and interviews with the customers key stakeholders and subject matter experts. Setup interviews with the key stakeholders, such as server administrators, infrastructure managers, security managers, service delivery managers, and so on. Find out who is responsible for business continuity and disaster recovery. At one of my recent customer engagements there was a requirement to implement private VLANs for a backup solution. This is all part of the requirements gathering, and drives some of the technical decisions that you’ll make during the design itself. In my case, I had to implement the Cisco Nexus 1000V rather than the VMware Distributed Virtual Switch, as there was technical configuration limitation using the DVS with Cisco UCS Fabric Interconnects in End-Host mode.
Understanding security requirements will also be an important area to feed into the design, so be mindful of this during the exam. Do they need to be compliant with any governance or compliance? For instance, you may find during the requirement gathering phase that ‘Lockdown Mode’ must be enabled to satisfy a security requirement. This may affect another requirement to enable SSH access to each host, or use the vMA to manage hosts directly. See where this is going?
This topic will come up at some stage during interaction with the customer. It’s also in objective 2.1 of the exam blueprint, so make sure you understand this!
A functional requirement is what the design must DO. A non-functional requirement typically describes HOW is does it. Lets take a couple of examples:
The design must cater for 10% growth in storage capacity used by Engineering, and 30% compute growth, within the next 12 months
This is a functional requirement. In other words the design must deliver on 10% growth in storage (something the design must DO or ACHIEVE).
The design must incorporate storage from the existing EMC VNX storage array”
This is a non-functional requirement, but also a constraint. The vSphere design must use existing storage, but this introduces a constraint. The existing storage array may not have enough capacity for 10% growth for Engineering. We now have a Risk too!
Something else you should familiarise yourself with is the use of methodologies such as ITIL to map service dependancies, or define capacity management plans for example, in addition to tools such as VMware Capacity Planner. Be mindful of this as the VCAP-DCD5 exam is likely to test you on these areas. Conceptual, Logical and Physical Design
For the remainder of blueprint Section 1 (Conceptual Design), focus on the first chapter of the vSphere 5 Design Workshop course book. Make sure you understand this section as it flows through the VCAP-DCD5 exam.
Still having trouble understanding the difference between Conceptual, Logical and Physical? Read this.
Another reason to attend the vSphere 5: Design Workshop course is to understand the VMware Architecture Framework and how to apply this to a design. You will be expected to understand how the design framework can be applied, in essence using the following qualifiers:
An example of this is understanding recovery for example and how RTO (Recovery Time Objective) and RPO (Recovery Point Objective) are used in a design, in particular being able to obtain these from the requirements gathering phase.
If you have created designs before then I’m sure you have spent many hours in Visio creating diagrams that illustrate the facets of your design. As stated on the exam blueprint, you will be asked to use a design tool to produce such as diagram. If you struggle with these then make sure you practice in Visio or Google Drive (Drawing) prior to the exam. Practice this first, and check out the demo here.
VMware have made available a Cloud Infrastructure Architecture Case Study, which I found extremely valuable throughout the VCAP5-DCD study. Whilst it is a case-study, it also follows the VMware design methodology and provides an excellent grounding to base your own designs from.
This is just an start, and by no means a comprehensive study guide. I’ve summarised the blueprint sections below, so take your time on each one and don’t just dismiss it thinking, “Ah, this Risks, Contraints and Assumptions thing, won’t be that hard…”, because it WILL catch you out!
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