I have been working in critical facilities for over 35 years including the commercial nuclear power industry, aerospace, a financial institute, and in the professional services realm. For the last 10-plus years I have been involved with providing third-party commissioning services and facilities management consulting. One thing that has become sometimes painfully apparent is there is often a conflict between achieving the desired level of reliability without over complicating the matters at hand. This concept applies to more than just the infrastructure topology, but throughout most all aspects of facility operations and maintenance.
If you look at the evolution of critical facilities you will see a fairly consistent increase in complexities as the requirements and expectation of sustaining continuous operations became more and more demanding. When I first started working in data centers in the mid-1980s, static uninterruptible power systems (UPS) were just beginning to be the norm and sites still required annual outages to perform critical maintenance activities. In many instances, maintenance staff were required to perform “energized work” where staff would have to perform re-torqueing of connections while the gear was still energized. Even so most sites had to shut down for the main utility “triennial” switchgear maintenance.