User's Manual

222 Power Management
consumption and limit it to within a few watts of the allocated power. Under
heavy load the server’s processors may be throttled to ensure power
consumption stays below or at allocation.
The M1000e enclosure can supply enough power for peak performance of
most server configurations, but many available server configurations will not
consume the maximum power that the enclosure can supply. To help data
center facilities provision power for their enclosures, the M1000e allows
customer to specify a System Input Power Cap to ensure overall chassis AC
power draw stays under a given threshold. The CMC first ensures enough
power is available to run the fans, IO Modules, iKVM (if present), and the
CMC itself. This power allocation is called the Input Power Allocated to
Chassis Infrastructure. Once the servers in an enclosure are powered up, any
attempt by the user to set the System Input Power Cap lower than the power
required to operate the servers at peak performance will fail.
If necessary for the total power budget to stay below the value of the System
Input Power Cap, the CMC will allocate servers a value less than their
maximum requested power. Servers are allocated power based on their
Priority setting, with priority 1 servers getting maximum power before the
priority 2 servers, and so on.
Configuration changes can occur in a modular enclosure that may require the
System Input Power Cap to be increased to allow the power up of additional
servers. Power needs in a modular enclosure increase when thermal conditions
change and the fans are needed to run at higher speed, which causes them to
consume additional power. Insertion of I/O modules, iKVM and additional
servers increases the power needs of the modular enclosure. A fairly small
amount of power is consumed by servers even when they are off to keep the
management controller powered up. Additional servers can be powered up in
modular enclosure only if sufficient power is available. The System Input
Power Cap can be increased any time up to a maximum value of 7928 watts
to allow the power up of additional servers.
Changes in modular enclosure that reduce the power allocation are server
power off, server removal, I/O module removal, iKVM removal and transition
of chassis to a powered off state. System Input Power Cap value of the chassis
can be re-configured when chassis is either ON or OFF.