User's Manual

250 Power Management
NOTE: In the event of a single PSU failure in this configuration, the two remaining
PSUs in the failing grid are marked as Online. In this state, either of the remaining
PSUs can fail without interrupting operation of the system. If a PSU fails, the chassis
health is marked non-critical. If the smaller grid cannot support the total chassis
power allocations, AC redundancy status is reported as No Redundancy and
Chassis health is displayed as Critical.
NOTE: The chassis needs only 3 PSUs to operate all blades. However, there must
be a balanced set of PSUs to support AC Redundancy; half of them are considered
when calculating power capacities; the other half are marked for AC redundancy.
If you install less than the number of PSUs required to operate your servers,
redundancy may be reported as No Redundancy or servers may not be
allowedtopower on.
Power Supply Redundancy Mode
The power supply redundancy mode is useful when redundant power grids are
not available, but you may want to be protected against a single PSU failure
bringing down your servers in a modular enclosure. One PSU's capacity over
the allocation requirements is kept in online reserve for this purpose.
This forms a Power Supply redundancy pool.
Any PSU installed outside this pool is not used. These PSUs join the
redundancy pool if any PSU in the pool fails.
Power Supply Redundancy Levels
CMC supports three levels of Power Supply Redundancy—1+1, 2+1,
and 3+1. This option keeps the additional PSU engaged at all times to
ensure that the failure of a single PSU can always be tolerated. Although
Figure 8-4 illustrates a configuration of four PSU present in the first four
PSU slots, CMC does not require the four PSU units to be present in
any specific PSU slot positions.
Dynamic Power Supply Engagement (DPSE) allows PSUs to be placed in
standby.
The standby state indicates a physical state (OFF). When you enable DPSE,
the extra PSUs are placed in Standby mode to increase efficiency and
save power.