Server Slot Power Priority Settings - Dell EMC PowerEdge VRTX User Manual

iDRAC provides CMC with its power envelope requirements before powering up the server. The power envelope consists of the
maximum and minimum power requirements necessary to keep the server operating. iDRAC's initial estimate is based on its initial
understanding of components in the server. After operation commences and further components are discovered, iDRAC may
increase or decrease its initial power requirements.
When a server is turned on in an enclosure, the iDRAC software reestimates the power requirements and requests a subsequent
change in the power envelope.
CMC supplies the requested power to the server, and the allocated wattage is subtracted from the available budget. After the server
is granted a power request, the server's iDRAC software continuously monitors the actual power consumption. On the basis of
actual power requirements, the iDRAC power envelope may change over a period of time. iDRAC requests a power step up if the
servers are fully using the allocated power.
Under heavy load, the performance of the processors on the server may be degraded to ensure power consumption stays lower
than the user-configured System Input Power Cap.
The PowerEdge VRTX enclosure can supply enough power for peak performance of most server configurations, but many available
server configurations do not consume the maximum power that the 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.
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