HP ProLiant Server Power Management for Red Hat Enterprise Linux 6.x
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Abstract
Power management is crucial to data center power provisioning. This document provides a brief overview of the
processor-based power saving features supported on HP ProLiant servers and the power management features such as
Power Regulator, Power Capping and Collaborative Power Control that are embedded in the ProLiant platforms. This
document also discusses how these features are used and their relationship to the Red Hat Enterprise Linux (RHEL) 6.x
(6.0, 6.1, 6.2 and 6.3) operating system, including new features available with ProLiant Gen8 Intel-based servers and
RHEL 6.x.
Introduction
The RHEL 6.x operating system and the HP ProLiant servers together use processor-based features to achieve better
power efficiency for processors. The processor-based features include:
Performance states (P-states) define a set of fixed operating frequencies and voltages, where P0 represents the
highest operating frequency and voltage. You can save power by entering P-states with lower frequency and voltage
levels. Either the platform firmware or the operating system controls the P-states.
Power states (C-states), excluding the C0 state, represent idle states and determine the power consumed when a
processor is idle. C0 is a non-idle state with higher C-states representing idle conditions with increasing power
savings. The operating system controls the C-states.
Throttle states (T-states) define a set of fixed frequency percentages which can be used to regulate the power
consumption and the thermal properties of the processor. ProLiant systems may reserve the use of T-states for the
system firmware.
In addition, ProLiant servers are also capable of using the various processor states to support innovative power
management features that are operating system independent and are implemented in the hardware and firmware:
HP Power Regulator provides a facility to efficiently control processor power usage and performance, either statically
or dynamically depending on the mode selected.
HP Power Capping allows an administrator to limit the power consumed by a server.
HP Dynamic Power Capping has the additional feature of ensuring that the power limit set by an administrator is
maintained by reacting to a spike in server workload more rapidly than basic HP Power Capping.
The Power Regulator and Power Capping technologies are designed to work in conjunction with each other. To make the
operating system aware of Power Capping, HP provides the Collaborative Power Control technology. This is a two-way
communication mechanism established between the operating system and platform firmware, and can be used by the
operating system and hardware collaboratively to choose the appropriate performance level for the server. Support for
this technology is present in both RHEL 6.x and on ProLiant Gen8 servers.
HP Power Regulator
HP Power Regulator is a configurable processor power usage feature which allows you to choose from several options
for the server to manage P-states or to delegate control of regulating P-states to the operating system.
HP Power Regulator is implemented within the firmware on both Intel-based and AMD-based ProLiant servers.
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ProLiant
servers provide the following HP Power Regulator modes, that you can select from the ROM Based Setup Utility (RBSU)
or through HP iLO 4:
HP Dynamic
The firmware is capable of managing the P-states. However, when the Collaborative
Power Control (CPC) setting is enabled in RBSU, the OS and the firmware collaborate to
attain the desired frequency for a processor. When CPC is disabled, this mode allows the
firmware to exclusively control the P-states of a processor to match the server load. On
HP ProLiant Gen8 servers, HP Dynamic is the default mode with the CPC setting enabled.
HP Static Low
The firmware controls the P-states. The P-state of the processor is static and it is set to
the P-state which corresponds to the lowest operating frequency supported by the
processor.
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For detailed information on HP Power Regulator support across the different generations of ProLiant platforms, see:
http://h18013.www1.hp.com/products/servers/management/ilo/sup_servers.html