new power saving feature in W2008 R2 (source: Elearning)

Windows Server 2008 R2 introduces significant advancements in server power management capabilities. The Processor Power Management (PPM) engine in Windows Server 2008 R2 is rewritten and improved, and there are additional power-management Group Policy settings that help to fine-tune the processor’s speed and power consumption to match current demands. New parameters for PPM further improve the power efficiency. You can use features such as Core Parking, reduced processor power consumption, centralized storage, and Intelligent Timer Tick Distribution in virtualization scenarios to maximize the power efficiency of virtualized environments and physical systems.




Windows Server 2008 R2 reduces processor power consumption in server computers with multicore processors by using the Core Parking feature. The Core Parking feature enables Windows Server 2008 R2 to reduce multicore processor power consumption by consolidating processing onto fewer processor cores and suspending the inactive cores. The workload of every logical core in a server is tracked relative to all the others. The workloads of cores that are not being fully utilized can be suspended, and these workloads are then shifted to alternate cores. Keeping the unutilized cores in an idle state reduces the system power consumption. When additional processing power is required, the system activates the idle processor cores to handle the increased processing requirements.



Windows Server 2008 R2 adjusts the processor speed by using Advanced Configuration and Power Interface (ACPI) "P-states" of processors and reduces server power consumption. ACPI “P-states” are the processor performance states within the ACPI specification. Depending on the processor architecture, Windows Server 2008 R2 can adjust the P-states of individual processors and provide control over power consumption.



Another strategy for reducing power used by individual servers is to centralize their storage by using a storage area network (SAN), which has a higher storage-capacity-to-power-consumption ratio than a typical server. SAN makes more efficient use of the available disk space, because any server can have access to the available storage on SAN. Windows Server 2008 R2 greatly improves access to storage on SANs and supports booting from a SAN, which eliminates the need for local hard disks in the individual server computers. As a result, power consumption decreases.



Windows Server 2008 R2 introduces Intelligent Timer Tick Distribution or Tick Skipping. This feature extends processor idle states or deep “C-states” by not activating the CPU unnecessarily, thus saving power. Only one processor handles the periodic system timer tick; other processors are signaled only when necessary. The amount of background work that is performed by the operating system is reduced in Windows Server 2008 R2. This allows processors to better utilize the deep “C-states”, in which the processor consumes very little energy, but requires time to return to an operational state