HP Power Capping and HP Dynamic Power Capping for ProLiant servers

6
produce. However, the enclosure’s power supply array powers HP BladeSystem servers. For a blade server, the
maximum available power is the amount of power that the enclosure’s Onboard Administrator reserved for that
server blade. Both iLO and Insight Control report this value: iLO reports it as Power supply maximum power for ML
and DL servers and as Initial power-on request value for BladeSystem servers.
Minimum and maximum power consumption values for a server can change slightly while the server is running.
During normal operations, iLO and the power management system continue to check both the 10-second average
and the peak power readings for the server. iLO will raise the maximum power consumption level if it measures a
peak value above the established maximum. iLO will lower the minimum power consumption if it reads an average
power value that is below the present minimum.
Differences between HP Dynamic Power Capping and HP Power
Capping
Both HP Dynamic Power Capping and HP Power Capping maintain a server’s power consumption at or below the
cap value set by an administrator. HP Dynamic Power Capping monitors power consumption and maintains a
server’s power cap much faster than HP Power Capping. Table 3 provides a quick architectural and operational
comparison of HP Dynamic Power Capping and HP Power Capping. To avoid confusion between the two, we will
refer to HP Power Capping as basic Power Capping throughout the remainder of this paper.
Table 3. Characteristics of Dynamic Power Capping and basic Power Capping
Dynamic Power
Capping
Basic Power Capping
Power capping
executed from
Power management
microcontroller
iLO and system ROM
BIOS
Control of processor
power
Direct hardware
connection to
processor to control P-
state/clock throttling at
the processor
hardware level
Firmware control of P-
state/clock throttling
through processor
registers
Power monitoring cycle More than 5 times per
second
Once every 5 seconds
Time to bring server
power consumption
back under its cap
Less than 0.5 seconds 10 – 30 seconds
Intended application Managing power and
cooling provisioning
Managing cooling
provisioning
Power provisioning and Dynamic Power Capping
Basic Power Capping does an excellent job of maintaining average server power utilization at or below a cap
value. Administrators can use it to help manage data center cooling requirements: Limiting server power
consumption fast enough can prevent excessive heat generation. However, as the information in Table 3 illustrates,
basic Power Capping cannot respond quickly enough to limit sudden increases in server power consumption that
could trip an electrical circuit breaker.
Dynamic Power Capping operates more than 25 times faster than basic Power Capping. Dynamic Power Capping
can bring a server experiencing a sudden workload increase back under its power cap in less than one-half second.
This is fast enough to prevent any surge in power demand that could cause a typical data center circuit breaker to