User's Manual

increased PSU life, and reduced heat generation. To use this feature, you must have an Enterprise
License.
CMC monitors total enclosure power allocation, and moves the PSUs into Standby state, causing the total
power allocation of the chassis to be delivered through fewer PSUs. As the online PSUs are more efficient
when running at higher utilization, it improves their efficiency and longevity of the standby PSUs.
To operate remaining PSUs at their maximum efficiency, use the following power redundancy modes:
• PSU Redundancy mode with DPSE provides power efficiency. At least two supplies are online, with
one PSU required to power the configuration, and one to provide redundancy in case of a PSU failure.
PSU Redundancy mode offers protection against the failure of any one PSU, but offers no protection
in the event of an AC grid loss.
• Grid Redundancy mode with DPSE, where at least two PSUs are active, one on each power grid. Grid
redundancy also balances the efficiency and maximum availability for a partially-loaded modular
enclosure configuration.
• Disabling DPSE provides the lowest efficiency as all four supplies are active and share the load,
resulting in lower utilization of each power supply.
DPSE can be enabled for all two power supply redundancy configurations explained above — Power
Supply Redundancy, and Grid Redundancy.
NOTE: In a two PSU configuration modes, server load may prevent any PSU from changing to the
Standby mode.
• In a Power Supply Redundancy configuration, in addition to the PSUs required to power the
enclosure, the enclosure always keeps an additional PSU powered on and marked Online. Power
utilization is monitored and one PSU can be moved to Standby state on the basis of overall system
load. In a four PSU configuration, a minimum of two PSUs are always turned on.
Because an enclosure in the Power Supply Redundancy configuration always has an extra PSU
engaged, the enclosure can accommodate the loss of one online PSU and still have enough power
for the installed server modules. The loss of the online PSU causes 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 turning on.
• In Grid Redundancy configuration, all PSUs are engaged when the chassis is turned on. Power
utilization is monitored, and if system configuration and power utilization allows, PSUs are moved to
the Standby state. Because 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 Grid Redundancy configuration cause the engagement of PSUs
from the Standby state. This maintains the mirrored configuration needed for dual-grid redundancy.
NOTE: With DPSE in enabled state, if power demand increases in both the two Power
Redundancy policy modes, the standby PSUs are brought Online to reclaim power.
Default Redundancy Configuration
As shown in the table here, the default redundancy configuration for a chassis depends on the number of
PSUs that it contains.
Table 27. Default Redundancy Configuration
PSU Configuration Default Redundancy Policy Default Dynamic PSU Engagement Setting
Two PSUs DC Redundancy Disabled
Four PSUs DC Redundancy Disabled
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