User's Manual

288 Power Management
When you configure a system for AC redundancy, the PSUs are divided into
grids: PSUs in slots 1, 2, and 3 are in the first grid while PSUs in slots 4, 5, and
6 are in the second grid. The CMC manages power so that if there is a failure
of either grid the system will continue to operate without any degradation.
AC redundancy also tolerates failures of individual PSUs.
NOTE: Since one role of AC redundancy is to provide seamless server operation
despite failure of a whole power grid thus the most power is available to maintain
AC redundancy when the capacities of the two grids are approximately equal.
NOTE: AC redundancy is only met when the load requirements do not exceed the
capacity of the weakest power grid.
AC Redundancy Levels
One PSU in each grid is the minimum configuration necessary for use as AC
redundant. Additional configurations are possible with every combination
that has at least one PSU in each grid. However, to make the maximum power
available for use, the total power of the PSUs in each leg should be as close to
equal as practical. The upper limit of power while maintaining AC
redundancy is the power available on the weakest of the two grids.
If for some reason the CMC is unable to maintain AC redundancy then E-
mail and/or SNMP alerts are sent to administrators if the Redundancy Lost
event is configured for alerting.
Figure 9-1. Figure 8-2. 2 PSUs per grid and a power failure on grid 1
Power
Supply
#1
Power
Supply
#2
Empty
Slot
#3
Power
Supply
#4
Power
Supply
#5
Empty
Slot
#6
AC Power Grid #1
AC Power Grid #2
Chassis DC Power Bus