White Paper - Power Management in Intel Architecture Servers

Working Together
Interactions and Usage Models
Several applications can benefit from the boosted frequency that is
higher than the marked frequency of the CPU. Turbo mode increases
in performance in multi-threaded and single-threaded workloads by
increasing the frequency, while DBS can reduce power when a higher
CPU performance is not needed. Node Manager allows a server to
stay within pre-determined power limits, similar to a car having an
automatic gear-shifting system, as shown in Figure 7.
The combination of all these power management technologies
enables a user to get the performance boost when needed, but at
other times to save on both the energy needed to run a server and the
air conditioning needed to remove the heat generated by the server.
The best way to achieve a server’s optimal power performance is
to turn ON the DBS and turbo modes in BIOS whenever available,
and then use management software to determine the appropriate
power policies that can be implemented through NM. One strategy
is to run the servers at full power during the day when many server
applications are in use, reduce the power during the evening when
the workload decrease, and run at the lowest level nights and
weekends. Another strategy is to monitor the power of all servers
in the rack, and if the overall circuit-breaker power is close to being
reached, apply lower power limits for the subset of servers that are
not running mission-critical applications at that time. This will enable
a higher compute density to be available in the rack above the power
limits, allowing different servers to run faster at different times of
the day or night.
It has been shown that for a single server, up to a 40W savings can
be achieved without a performance impact when an optimal power
management policy is applied [2]. To determine the optimum policy, it
is advisable to understand the application and workload needs, as well
as monitor the server usage patterns, over a period of time before
setting different limits in the NM. However, DBS and turbo modes
should always be turned ON whenever available.
Enterprise Management Software
Node Manager
Turbo
Temperature
Demand Based Switching
Figure 7. An analogy with a car where extra power may be needed to climb a hill, but reduced power when running idle or low loads�
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White Paper: Power Management in Intel® Architecture Servers