User's Manual

260 Power Management
New Server Engagement Policy
When a new server is powered on, the CMC may need to decrease power to
lower priority servers to allow more power for the new server if adding the new
server exceeds the power available for the chassis. This could happen if the
administrator has configured a power limit for the chassis that is below what
would be required for full power allocation to the servers, or if insufficient
power is available for the worst-case power need of all servers in the chassis.
If enough power cannot be freed by reducing the allocated power of the lower
priority servers, the new server may not be allowed to power up.
The highest amount of sustained power required to run the chassis and all of
the servers, including the new one, at full power is the worst-case power
requirement. If that amount of power is available, then no servers are
allocated power that is less than the worst-case power needed and the new
server is allowed to power up.
If the worst-case power requirement cannot be met, power is reduced to the
lower priority servers until enough power is freed to power up the new server.
Table 8-2 describes the actions taken by the CMC when a new server is
powered on in the scenario described above.
If a PSU fails, it results in a non-critical health state and a PSU failure event is
generated. The removal of a PSU results in a PSU removal event.
If either event results in a loss of redundancy, based on power allocations,
a loss of redundancy event is generated.
If the subsequent power capacity or the user power capacity is greater than
the server allocations, servers will have degraded performance or, in a worse
case, servers may be powered down. Both conditions are in reverse-priority
order, that is, the lower priority servers are powered down first.
Table 8-2. CMC Response When a Server Power-On is Attempted
Worst Case Power
is Available
CMC Response Server
Power On
Yes No power conservation is required Allowed
No Perform power conservation:
• Power required for new server is available
• Power required for new server is not available
Allowed
Disallowed