Energy Management for Commercial Servers

I n the past, energy-aware computing was primarily associated with mobile and embedded computing platforms. Servers—high-end, multiprocessor systems running commercial workloads—typically included extensive cooling systems and resided in custom-built rooms for high-power delivery. In recent years, however, as transistor density and demand for computing resources have rapidly increased, even high-end systems face energy-use constraints. Moreover, conventional computers are currently air cooled, and systems are approaching the limits of what manufacturers can build without introducing additional techniques such as liquid cooling. Clearly, good energy management is becoming important for all servers. Power management challenges for commercial servers differ from those for mobile systems. Techniques for saving power and energy at the circuit and microarchitecture levels are well known, and other low-power options are specialized to a server’s particular structure and the nature of its workload. Although there has been some progress, a gap still exists between the known solutions and the energy-management needs of servers. In light of the trend toward isolating disk resources in separate cabinets and accessing them through some form of storage networking, the main focus of energy management for commercial servers is conserving power in the memory and microprocessor subsystems. Because their workloads are typically structured as multiple-application programs, system-wide approaches are more applicable to multiprocessor environments in commercial servers than techniques that are primarily applicable to single-application environments, such as those based on compiler optimizations.