User's Manual

200 Power Management
AC Redundancy
For AC Redundancy mode to operate at optimal power, you must have six
PSUs in your chassis. You can set your chassis 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. Three of the PSUs
connect to one AC power grid, while the other three connect to another AC
power grid. When the system is running optimally in AC Redundancy mode,
all the PSUs share the load.
NOTICE: To avoid a system failure and for AC Redundancy to work effectively, you
must ensure that each set of PSUs is connected to a separate AC grid.
In case one AC grid fails, the three PSUs on the functioning AC grid take over
without interruption to the servers or infrastructure.
NOTICE: 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
The capacity of the highest-rated PSU in the chassis is kept as a spare,
ensuring that a failure of any one PSU will not cause the servers or chassis to
power-down.
Power Supply Redundancy mode does not utilize all six PSUs; it uses
maximum of four and a minimum of two.
Failure of two PSUs may cause some or all servers in the chassis to power
down.
Table 8-2. Default Redundancy Configuration
PSU Configuration Default Redundancy
Policy
Default Dynamic PSU Engagement
Setting
Six PSUs AC Redundancy Disabled
Three PSUs No Redundancy Disabled