Users Guide
enclosure can supply. To help datacenters allocate power for their enclosures, the PowerEdge VRTX
allows you to specify a System Input Power Cap to make sure that the overall chassis AC power draw
stays within a given threshold point. CMC first makes sure that enough power is available to run the fans,
I/O module, storage adapters, physical disk drive, main board, and CMC itself. This power allocation is
called the Input Power Allocated to Chassis Infrastructure. After Chassis infrastructure, the servers in an
enclosure are turned on. Any attempt to set a System Input Power Cap less than the “Power Burden” will
not be successful. Power Burden is the sum of power allocated to the infrastructure and the minimum
power allocated for the powered servers.
NOTE: To use the Power Cap feature, you must have an Enterprise License.
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-one
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, shared HDDs, or PCIe cards 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 module and storage adapters, PCIe cards, physical disk, main
board; number, type, and configuration of PSUs also increase 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 5000 Watt to allow the
power up of additional servers.
Changes in the modular enclosure that reduce the power allocation are:
• Server turned off
• I/O module turned off
• Storage adapters, PCIe cards, physical disk drive, and main board turned off
• Transition of the chassis to a turned-off state
You can reconfigure the System Input Power Cap when the chassis is either turned on or turned off.
Server Slot Power Priority Settings
CMC allows you to set a power priority for each of the four 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
priority of the slots 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
169