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Draft Document for Review October 14, 2014 10:19 am
2.13 Energy management
The Power E870 and Power E880 systems have features to help clients become more energy
efficient. EnergyScale technology enables advanced energy management features to
conserve power dramatically and dynamically and further improve energy efficiency.
Intelligent Energy optimization capabilities enable the POWER8 processor to operate at a
higher frequency for increased performance and performance per watt, or dramatically
reduce frequency to save energy.
2.13.1 IBM EnergyScale technology
IBM EnergyScale technology provides functions to help the user understand and dynamically
optimize processor performance versus processor energy consumption, and system
workload, to control IBM Power Systems power and cooling usage.
EnergyScale uses power and thermal information that is collected from the system to
implement policies that can lead to better performance or better energy usage. IBM
EnergyScale has the following features:
Power trending
EnergyScale provides continuous collection of real-time server energy consumption. It
enables administrators to predict power consumption across their infrastructure and to
react to business and processing needs. For example, administrators can use such
information to predict data center energy consumption at various times of the day, week,
or month.
Power saver mode
Power saver mode lowers the processor frequency and voltage on a fixed amount,
reducing the energy consumption of the system while still delivering predictable
performance. This percentage is predetermined to be within a safe operating limit and is
not user configurable. The server is designed for a fixed frequency drop of almost 50%
down from nominal frequency (the actual value depends on the server type and
configuration).
Power saver mode is not supported during system start, although it is a persistent
condition that is sustained after the boot when the system starts running instructions.
Dynamic power saver mode
Dynamic power saver mode varies processor frequency and voltage based on the usage
of the POWER8 processors. Processor frequency and usage are inversely proportional for
most workloads, implying that as the frequency of a processor increases, its usage
decreases, given a constant workload. Dynamic power saver mode takes advantage of
this relationship to detect opportunities to save power, based on measured real-time
system usage.
When a system is idle, the system firmware lowers the frequency and voltage to power
energy saver mode values. When fully used, the maximum frequency varies, depending
on whether the user favors power savings or system performance. If an administrator
prefers energy savings and a system is fully used, the system is designed to reduce the
maximum frequency to about 95% of nominal values. If performance is favored over
energy consumption, the maximum frequency can be increased above the nominal
frequency for extra performance. Table 2-33 on page 106 shows the maximum frequency
boost available for different speed processors in the Power E870 and E880
Chapter 2. Architecture and technical overview
5137ch02.fm
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