Reliability of Data Centers by Tier Classification

When the concept of reliability began to formally become an integrated engineering approach in the 50s, reliability was associated with failure rate. Today the term “reliability” is used as an umbrella definition covering a variety of subjects including availability, durability, quality, and sometimes the function of the product. Reliability engineering was developed to quantify “how reliable” a component, product, or system was when used in a specific application for a specific period of time. The data center industry has come to rely on “tier classifications” as presented in a number of papers by the Uptime Institute as a gradient scale of data center configurations and requirements from least (Tier 1) to most reliable (Tier 4). This paper will apply the principles and modeling techniques of reliability engineering to specific examples of each of the tier classifications and discuss the results. A review of the metrics of reliability engineering being used will also be included.