User's Manual

296 Power Management
Redundancy Policies
Redundancy policy is a configurable set of properties that determine how the
CMC manages power to the chassis. The following redundancy policies are
configurable with or without dynamic PSU engagement:
• AC Redundancy
• Power Supply Redundancy
• No Redundancy
The default redundancy configuration for a chassis depends on how many
PSUs it contains, as shown in Table 9-1.
AC Redundancy
In AC Redundancy mode with six PSUs, all six PSUs are 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.
If one AC grid fails, the PSUs on the functioning AC grid take over without
interruption to the servers or infrastructure.
CAUTION: In AC redundancy mode, you must have balanced sets of PSUs (at least
one PSU in each grid). If this condition is not met, AC redundancy may not be
possible.
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 does not cause the servers or
chassis to power-down. Power Supply Redundancy mode requires up to four
PSUs. Additional PSUs, if present, will be utilized to improve power
efficiency of the system if DPSE is enabled. Subsequent failures after loss of
redundancy may cause the servers in the chassis to power down.
Table 9-1. Default Redundancy Configuration
PSU Configuration Default Redundancy
Policy
Default Dynamic PSU Engagement
Setting
Six PSUs AC Redundancy Disabled
Three PSUs No Redundancy Disabled