Users Guide

Infrastructure. Following Chassis Infrastructure, the servers in an enclosure are powered up. Any attempt
to set a System Input Power Cap less than the actual consumption fails.
If necessary for the total power budget to stay below the value of the System Input Power Cap, CMC
allocates servers a value less than their maximum requested power. Servers are allocated power based on
their Server Priority setting, with higher priority servers getting maximum power, priority 2 servers getting
power after priority 1 servers, and so on. Lower priority servers may get less power than priority 1 servers
based on System Input Max Power Capacity and the user-configured setting of System Input Power Cap.
Configuration changes, such as an additional server in the chassis, may require the System Input Power
Cap to be increased. Power needs in a modular enclosure also increase when thermal conditions change
and the fans are required to run at higher speed, which causes them to consume additional power.
Insertion of I/O modules and iKVM also increases the power needs of the modular enclosure. A fairly
small amount of power is consumed by servers even when they are powered down to keep the
management controller powered up.
Additional servers can be powered up in the modular enclosure only if sufficient power is available. The
System Input Power Cap can be increased any time up to a maximum value of 16685 watts to allow the
power up of additional servers.
Changes in the modular enclosure that reduce the power allocation are:
• Server power off
• Server
• I/O module
• iKVM removal
• Transition of the chassis to a powered off state
You can reconfigure the System Input Power Cap when chassis is either ON or OFF.
Server Slot Power Priority Settings
CMC allows you to set a power priority for each of the sixteen server slots in an enclosure. The priority
settings are 1 (highest) through 9 (lowest). These settings are assigned to slots in the chassis, and the
slot's priority is inherited by any server inserted in that slot. CMC uses slot priority to preferentially budget
power to the highest priority servers in the enclosure.
According to the default server slot priority setting, power is equally apportioned to all slots. Changing
the slot priorities allows administrators to prioritize the servers that are given preference for power
allocations. If the more critical server modules are left at their default slot priority of 1, and the less critical
server modules are changed to lower priority value of 2 or higher, the priority 1 server modules is
powered on first. These higher priority servers get their maximum power allocation, while lower priority
servers may be not be allocated enough power to run at their maximum performance or they may not
even power on at all, depending on how low the system input power cap is set and the server power
requirements.
If an administrator manually powers on the low priority server modules before the higher priority ones,
then the low priority server modules are the first modules to have their power allocation lowered down
to the minimum value, in order to accommodate the higher priority servers. Therefore, after the available
power for allocation is exhausted, then CMC reclaims power from lower or equal priority servers until
they are at their minimum power level.
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