Jan 21, 2015 | Blogs, Resources

The Notion of Dependency

By Craig McLellan

I have a very deep expertise in data centre relocations. Over the past 15 years, I’ve been directly involved in or managed at least 250 such projects.

What I’ve realized is that disaster recovery planning and data centre relocation experience very similar cycles. Both are filled with trepidation and a never-ending parade of naysayers. In fact, the only difference is the planner’s vision of the outcome. In relocations, those charged with organizing the move know it will happen and who will be involved while the people preparing for a disaster hope it will never happen and might prefer to be away when it does.

The outcome needs to be the same – success. Through much trial and error I have also learned that regardless of the technology or nature of the business the plan must be executed with as little interruption as possible.

When starting, application interdependence is the Achilles heel — it’s the “I don’t know that I don’t know” circumstance. Early in my career I fortunately worked for a successful network integrator. I learned that a network by its very nature should not contain a single point of failure and that its performance was determined by the collective health of its components or in a broader sense the dependencies between its components.

In planning data centre moves, I quickly realized that dependencies were the real issue. Know what application is dependent on what other application and immediately there is a path through any problem. By creating my own rudimentary interdependency analysis tools, we could identify problems we didn’t know existed. Often developers wrongfully believe it’s clever to build in a high degree of interdependency.

More often than not these “tools” were really just the outcomes of extensive developer interviews – asking how application A relates to application B. However, if a developer creates an undocumented dependency and one fails then it’s going to be difficult to plan how to recover from such an oversight.

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