Effectiveness of Rack-Level Fans—Part II: Control Strategies and System Redundancy

Abstract

Fan efficiency is known to increase with size. In part I of this study, savings in server fan power on the order of 50% were reported by replacing server-enclosed 60 mm fans with a rear-mounted wall of larger fans (80 mm or 120 mm in size). A methodology for row-wise control of such rack-level fans, with the purpose of simulating an actual product, is previewed and savings comparable to part I are reported. Performance under real-life scenarios such as nonuniform computational loads and fan failure is investigated. Each rack-level setup has distinct advantages. Selecting between configurations would necessitate a compromise between efficiency, redundancy, and cost.