Users Guide

Figure 8. Chassis With Six-PSU Configuration
CMC maintains a power budget for the enclosure that reserves the necessary wattage for all installed
servers and components.
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
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