Users Guide

CMC allocates power to the CMC infrastructure and the servers in the chassis. CMC infrastructure consists of components in the
chassis, such as fans, I/O modules, and iKVM (if present). The chassis may have up to 16 servers that communicate to the chassis
through the iDRAC. For more information, see the iDRAC User’s Guide at support.dell.com/manuals.
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 powered-up in an enclosure, the iDRAC software re-estimates the power requirements and requests a subsequent
change in the power envelope.
CMC grants the requested power to the server, and the allocated wattage is subtracted from the available budget. Once the server
is granted a power request, the server's iDRAC software continuously monitors the actual power consumption. Depending on the
actual power requirements, the iDRAC power envelope may change over time. iDRAC requests a power step-up only if the servers
are fully consuming the allocated power.
Under heavy load the performance of the server’s processors may be degraded to ensure power consumption stays lower than the
user-configured System Input Power Cap.
The PowerEdge M1000e 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 data centers provision
power for their enclosures, the M1000e allows you to specify a System Input Power Cap to ensure that the overall chassis AC
power draw stays under a given threshold. CMC first ensures enough power is available to run the fans, IO Modules, iKVM (if
present), and CMC itself. This power allocation is called the Input Power Allocated to Chassis 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
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