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Host power management (HPM) on ESXi 5.0 saves energy by placing certain parts of a computer system or device into a reduced power state when the system or device is inactive or does not need to run at maximum speed. This feature can be used in conjunction with distributed power management (DPM), which redistributes VMs among physical hosts in a cluster to enable some hosts to be powered off completely.

The default power policy for HPM in vSphere 5 is “balanced,” which reduces host power consumption while having little or no impact on performance for most workloads. The balanced policy uses the processor’s P-states, which save power when the workloads running on the system do not require full CPU capacity.

A technical white paper has been published that describes:

  • What to adjust in your ESXi host’s BIOS settings to achieve the maximum benefit of HPM.
  • The different power policy options in ESXi 5.0 and how to set a custom policy.
  • Using esxtop to obtain and understand statistics related to HPM, including the ESXi host’s power usage, the processor’s P-states, and the effect of HPM on %USED and %UTIL.
  • An evaluation of the power that HPM can save while different power policies are enabled. The amount of power saved varies depending on the CPU load and the power policy.

For the full paper, see Host Power Management in VMware vSphere 5.

Note: Some performance-sensitive workloads might require the "high performance" policy.