Dell PowerEdge M1000e Chassis Management Controller Firmware Version 5.1 User’s Guide

Power Budgeting For Hardware Modules

CMC offers a power budgeting service that allows you to configure power budget, redundancy, and dynamic power for the chassis.

The power management service enables optimization of power consumption and re-allocation of power to different modules based on demand.

The following figure illustrates a chassis that contains a six-PSU configuration. The PSUs are numbers 1-6, starting on the left-side of the enclosure.

Figure 1. Chassis With Six-PSU Configuration 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 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: