Specifications

112 IBM Flex System p260 and p460 Planning and Implementation Guide
򐂰 Power Saver Mode
Power Saver Mode reduces the processor frequency and voltage by a fixed
amount, reducing the energy consumption of the system, while 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 50% from nominal. Power Saver Mode is not
supported during boot or reboot operations, although it is a persistent
condition that is sustained after the boot, when the system starts
executing instructions.
򐂰 Dynamic Power Saver Mode
Dynamic Power Saver Mode varies processor frequency and voltage, based
on the use of the POWER7 processors. This setting is configured from
BladeCenter Advanced Management Module or IBM Director Active Energy
Manager. Processor frequency and usage are inversely proportional for most
workloads, implying that, as the frequency of a processor increases, its use
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 Saver Mode values. When fully used, the maximum frequency
varies, depending on whether you favor power savings or system
performance. If energy savings are preferred and the system is fully used, the
system can reduce the maximum frequency to 95% of nominal values. If
performance is favored over energy consumption, the maximum frequency is
at least 100% of nominal.
Dynamic Power Saver Mode is mutually exclusive with Power Saver mode.
Only one of these modes can be enabled at one time.
򐂰 Power capping
Power capping enforces a limit, specified by you, on power usage. Power
capping is not a power-saving mechanism. It enforces power caps by
throttling the processors in the system, degrading performance significantly.
The idea of a power cap is to set a limit that is not expected to be reached, but
that frees up margined power in the data center. The margined power is the
amount of extra power allocated to a server during installation in a data
center. It is based on those server environmental specifications that usually
are never reached because server specifications are always based on
maximum configurations and worst case scenarios. The energy cap is set
and enabled in BladeCenter Advanced Management Module and in IBM
Systems Director Active Energy Manager.