Abstract; Introduction; Basics Of Server Power Control - Compaq BL10e - HP ProLiant - 512 MB RAM Introduction Manual

Abstract

This paper describes HP power capping technologies, including the original HP Power Capping and
HP Dynamic Power Capping. Both are power management features of HP ProLiant servers that
operate independently of the operating system (OS) and allow system administrators to manage the
power consumption of a server or group of servers. The paper outlines the use of power capping as
part of a planning and provisioning strategy in the data center. It also describes the relationship
between power capping and other power management tools such as HP Power Regulator. It is
assumed that the reader is familiar with ProLiant servers, the Integrated Lights Out (iLO 2)
management processor, and the Insight Power Manager (IPM) plug-in for HP Systems Insight Manager
(SIM).

Introduction

Today's high-performance servers are models of efficiency compared to previous generations. Server
performance-per-watt continues to increase steadily. However, the number of watts-per-server also
continues to climb steadily. These increases, combined with the increasing number of servers and
density in modern data centers, make planning and managing facility power and cooling resources
critically important. HP Power Capping and HP Dynamic Power Capping are ProLiant power
management tools designed to assist the data center administrator in these critical tasks.
Both HP Power Capping and HP Dynamic Power Capping are implemented in system hardware and
firmware and are therefore not dependent on the operating system or applications. Using the power
monitoring and control mechanisms built into ProLiant servers, power capping is specifically designed
to allow an administrator to limit, or cap, the power consumption of a server or group of servers. This
provides increased flexibility in data center planning by allowing the administrator to manage data
center parameters that are directly influenced by server power consumption, including data center
cooling requirements and electrical provisioning. Power capping also allows the administrator to
control server power consumption in emergency situations such as the loss of primary AC power.
It is important to understand that power capping does not reduce the total energy consumption
required for a server to accomplish a given computational workload. Power capping simply limits the
amount of power that a server can use at any point in time. This allows an administrator to more
efficiently allocate data center power and cooling resources. In general, if a given power cap restricts
the amount of power that the server would normally use in performing a task, then the execution of
that task will be prolonged. Seen over time, the server will consume about the same total energy to
execute the same computational workload.

Basics of server power control

The processor complex is one of the single greatest power consumers in ProLiant servers. In many
common configurations it is responsible for one-third of the power consumed by a server (Figure 1). It
also indirectly drives the power consumption of other server components. A busy processor naturally
increases the workload in both the memory and peripherals, and the heat generated by the increased
workload causes the fans to work harder.
All HP power management technologies take advantage of this processor-driven model to directly
control the processor's power consumption, thereby indirectly controlling overall server power
consumption. The power management system accomplishes this control using two separate
mechanisms: changing the processor P-state and throttling the processor clock.
3