In preparing for my recent VCDX Defense, I read a great deal of articles and a few books to better understand how to properly document and justify the design decisions I was making. One book in particular provided valuable insight that has helped me not just with the VCDX certification, but also in becoming a better Infrastructure Architect.
In IT Architect: Foundation in the Art of Infrastructure Design (Amazon link), the authors state:
“Design Decisions will support the project requirements directly or indirectly…When a specific technology is required to meet a design goal, justification is important and should be provided. With each design decision there is a direct, intended impact, but there are also other areas that may be affected…These options and their respective value can add quality to the design you make and provide insight into why you took a specific path.”
As I thought through the impact of each design decision, I tried to identify several key points, including:
After I had identified each of those key points, and in some cases multiple points, for each category I made sure they were properly documented. The book provided an example table to draw inspiration from, in addition Derek Seaman did as well on a blog article. I modified the examples to fit my writing style and then included a specific table for each design decision made at the end of each major section or heading within my architecture documentation.
An example of the table and categories showing the reasoning behind a set of design decisions from my VMware Integrated OpenStack VCDX Architecture document:
Now, when I need to revisit a design decision or another architect is reviewing the decisions within the design, there is additional information to provide insight into the thought process. It also helps to highlight what impact the decision has on the architecture as a whole.
Beyond the table and the relevant information for the design decision, it may be necessary to highlight the alternatives that were considered. As we know, there are usually multiple ways to meet a requirement — “showing your work” and being able to explain why you chose to do X versus Y in the VCDX Defense is an important aspect of the process. I found doing so within my documentation useful and you may find that to be true also.
The opinions expressed in this article are entirely my own and based solely on my own VCDX certification experience. They may or may not reflect the opinions of other VCDX certification holders or the VMware VCDX program itself.
Arrasjid, John Y., Mark Gabryjelski, and Chris McCain. “Chapter 2, Design Decisions.” IT Architect: Foundation in the Art of Infrastructure Design; a Practical Guide for IT Architects. Upper Saddle River, NJ: IT Architect Resource, 2016. 49. Print.