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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.
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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 36. Default Redundancy Configuration
PSU Configuration
Two PSUs
Four PSUs
Grid Redundancy
In Grid redundancy mode with four PSUs, all four PSUs are active. The two PSUs must connect to one AC power grid, while the
other two PSUs are connect to the other AC power grid.
CAUTION: To avoid a system failure, and for Grid redundancy to work effectively, there must be a balanced set of PSUs
properly cabled to separate AC grids.
If one AC grid fails, the PSUs on the functioning AC grid take over, without interrupting the servers or infrastructure.
CAUTION: In Grid redundancy mode, you must have balanced sets of PSUs (at least one PSU in each grid). If this
condition is not met, Grid redundancy is not 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 turn off. Power supply redundancy mode requires minimum two PSUs. Additional PSUs, if present,
are 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 turn off.
Power Budgeting For Hardware Modules
CMC offers a power budgeting service that allows you to configure power budget, redundancy, and dynamic power for the chassis.
The power management service enables optimization of power consumption and reallocation of power to different modules on the
basis of demand.
CMC maintains a power budget for the enclosure that reserves the necessary wattage for all installed servers and components.
CMC allocates power to the CMC infrastructure and the servers in the chassis. CMC infrastructure consists of components in the
chassis, such as fans, I/O module, and storage adapters, PCIe cards, physical disk, main board. The chassis may have up to four
servers that communicate to the chassis through an iDRAC. For more information, see the iDRAC User's Guide at dell.com/
support/manuals.
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Default Redundancy Policy
DC Redundancy
DC Redundancy
Default Dynamic PSU Engagement Setting
Disabled
Disabled
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