User's Manual

226 Power Management
AC Redundancy
For AC Redundancy mode to operate at optimal power, the chassis must
contain six PSUs. A chassis can be set to operate in AC Redundancy mode
with fewer than six PSUs, but it will operate in a degraded state.
In AC Redundancy mode, all six PSUs will be active. The three PSUs on the
left must connect to one AC power grid, while the three PSUs on the right
connect to another AC power grid.
CAUTION: To avoid a system failure and for AC Redundancy to work effectively, each set
of PSUs must be connected to a separate AC grid.
If one AC grid should fail, the three PSUs on the functioning AC grid take
over without interruption to the servers or infrastructure.
CAUTION: In AC Redundancy mode, a difference in the number of PSUs between
the two AC grids (for example, three PSUs on one AC grid and two on the other AC
grid) will cause a degradation in the redundancy.
Power Supply Redundancy
When power supply redundancy is enabled, a PSU in the chassis is kept as a
spare, ensuring that the failure of any one PSU will not cause the servers or
chassis to power-down. Power Supply Redundancy mode requires four PSUs
to operate correctly; any additional PSUs will not be utilized. Failure of two
PSUs may cause the servers in the chassis to power down.
No Redundancy
Power from up to three PSUs is used to power the entire chassis.
CAUTION: The No Redundancy mode uses only three PSUs without a backup.
Failure of one of the three PSUs being used could cause servers to lose power and
data.
Table 8-1. Default Redundancy Configuration
PSU Configuration Default Redundancy
Policy
Default Dynamic PSU Engagement
Setting
Six PSUs AC Redundancy Disabled
Three PSUs No Redundancy Disabled