Users Guide

Executing Power Control Operations Using RACADM
To perform power actions, use the serveraction command. For more information, see the iDRAC8 RACADM Command Line
Interface Reference Guide available at dell.com/support/manuals.
Power Capping
You can view the power threshold limits that covers the range of AC and DC power consumption that a system under heavy
workload presents to the datacenter. This is a licensed feature.
Power Capping in Blade Servers
Before a blade server powers up, iDRAC provides CMC with its power requirements. It is higher than the actual power
that the blade can consume and is calculated based on limited hardware inventory information. It may request a smaller
power range after the server is powered up based on the actual power consumed by the server. If the power consumption
increases over time and if the server is consuming power near its maximum allocation, iDRAC may request an increase of the
maximum potential power consumption thus increasing the power envelope. iDRAC only increases its maximum potential power
consumption request to CMC. It does not request for a lesser minimum potential power if the consumption decreases. iDRAC
continues to request for more power if the power consumption exceeds the power allocated by CMC.
After, the system is powered on and initialized, iDRAC calculates a new power requirement based on the actual blade
configuration. The blade stays powered on even if the CMC fails to allocate new power request.
CMC reclaims any unused power from lower priority servers and subsequently allocates the reclaimed power to a higher priority
infrastructure module or a server.
If there is not enough power allocated, the blade server does not power on. If the blade has been allocated enough power, the
iDRAC turns on the system power.
Viewing and Configuring Power Cap Policy
When power cap policy is enabled, it enforces user-defined power limits for the system. If not, it uses the hardware power
protection policy that is implemented by default. This power protection policy is independent of the user defined policy. The
system performance is dynamically adjusted to maintain power consumption close to the specified threshold.
Actual power consumption may be less for light workloads and momentarily may exceed the threshold until performance
adjustments are completed. For example, for a given system configuration, the Maximum Potential Power Consumption is 700W
and the Minimum Potential Power Consumption is 500W. You can specify and enable a Power Budget Threshold to reduce
consumption from its current 650W to 525W. From that point onwards, the system's performance is dynamically adjusted to
maintain power consumption so as to not exceed the user-specified threshold of 525W.
If the power cap value is set to be lower than the minimum recommended threshold, iDRAC may not be able maintain the
requested power cap.
You can specify the value in Watts, BTU/hr, or as a percentage (%) of the recommended maximum power limit.
When setting the power cap threshold in BTU/hr, the conversion to Watts is rounded to the nearest integer. When reading the
power cap threshold back, the Watts to BTU/hr conversion is again rounded in this manner. As a result, the value written could
be nominally different than the value read; for example, a threshold set to 600 BTU/hr will be read back as 601 BTU/hr.
Configuring Power Cap Policy Using Web Interface
To view and configure the power policies:
1. In iDRAC Web interface, go to Overview > Server > Power/Thermal > Power Configuration > Power Configuration.
The Power Configuration page is displayed.
The Power Configuration page is displayed. The current power policy limit is displayed under the Currently Active Power
Cap Policy section.
2. Select Enable under iDRAC Power Cap Policy.
3. Under User-Defined Limits section, enter the maximum power limit in Watts and BTU/hr or the maximum % of
recommended system limit.
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Monitoring and Managing Power