HP ProLiant SL2500 Scalable System - Manual (Page 39)

Power capping 39
Power capping
Power capping overview
HP Scalable System products, including HP ProLiant SL Series, HP Moonshot Series, and HP Apollo Series
provide a power capping feature that operates at the server enclosure level. The capping feature can be
activated using a stand-alone utility called PPIC.EXE that runs in the environment of one of the resident servers
in the chassis to be power capped. After a power cap is set for the enclosure, all the resident servers in the
enclosure will have the same uniform power cap applied to them until the cap is either modified or canceled.
With HP APM, the enclosure-level power capping feature can be expanded without the need to use the
PPIC.EXE utility. A global power cap can be applied to all enclosures with one HP APM command, or
different caps can be applied to user-defined groups by using flexible zones within the same rack.
NOTE: HP recommends configuring the HP APM so that it controls only one rack.
Power capping requirements
All nodes in the chassis must have iLO Scale Out or iLO Advanced License.
To support the HP APM power capping functionality, all tray nodes in the chassis must be rebooted after the
chassis firmware has been updated, (for the s6500 chassis, the required version is v4.3 or higher) and the
appropriate BIOS version has been flashed. A reboot is also required anytime you add iLO Scale Out or iLO
Advanced License to the node. Upgrading to future versions of chassis firmware or HP APM firmware does
not require a reboot of the node to support the power capping feature.
Power capping and measurement tolerance
The average chassis power level displayed by HP APM will not exceed 5% above the chassis power cap.
NOTE: The power baseline process is required for power capping functionality to work
properly. All servers must be powered on and running an expected typical workload before
starting the power baseline process. Because the baseline process will cap the servers briefly,
performance will be impacted while power is measured and the baseline established.
As with any measurement system, variations in temperature, input power, and system loads will impact the
accuracy of the power calculations. All power reading displayed by this utility will have a -/+ 5% tolerance.
However, meter errors can be both positive and negative, so guardband for meter tolerance, as a
percentage of the cap, can approach zero as the number of servers increases.
Invalidating a power baseline
Since power baselines are global, the HP APM monitors the domains for changes in server and power supply
presence when a power baseline has been established. If a change occurs (for example, if a new server is