Pursuing optimization in a data center is like pursuing success in a completely new venture: defining how and when you reach your goal can be difficult. The owner, architect and engineer each may define optimization differently, perhaps as a design with the minimum total cost of ownership or the one with the least environmental impact, the smallest footprint or the highest efficiency. Zhenyuan Wang, Ernst Scholtz, Alexandre Oudalov and Francisco Canales offer insights on the range of interrelated factors to consider when optimizing a data center and on what commonly are the two most important objectives: minimizing cost and maximizing energy efficiency.