User's Manual

Power Management 225
be moved to Standby state depending on overall system load. In a six PSU
configuration, a minimum of two power supply units are always powered
on, one in
Online state and one in Redundant state.
Since an enclosure in the
Power Supply Redundancy configuration always
has one extra PSU engaged, the enclosure can tolerate the loss of one
online PSU and still have enough power for the installed server modules.
The loss of the online PSU will cause a standby PSU to come online.
Simultaneous failure of multiple PSUs may result in the loss of power to
some server modules while the standby PSUs are powering up.
• In the six PSU
AC Redundancy configuration, all six power supplies are
engaged at chassis powerup, with three PSUs in
Online state and three in
Redundant state. Power capacity is monitored, and if power draw allows,
PSUs are moved to the
Standby state in pairs -- one from each AC grid.
Since the
Online status of PSUs in a grid mirrors that of the other grid, the
enclosure can sustain the loss of power to an entire grid with no
interruption of power to the enclosure.
An increase in power demand in the
AC Redundancy configuration will
cause the engagement of PSUs from the
Standby state in pairs -- one from
each AC Grid. This maintains the mirrored configuration needed for dual-
grid redundancy.
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
Redundancy policy can be configured for a chassis. The default redundancy
configuration for a chassis depends on how many PSUs it contains, as shown
in Table 8-1.