Users Guide

NOTE: In a three PSU conguration, server load may prevent any PSUs from transitioning to
Standby
• In a Power Supply Redundancy conguration, the enclosure always keeps an additional PSU powered on and marked Online in
addition to the PSUs required to turn on the enclosure. Power utilization is monitored and up to four PSUs could be moved to Standby
state depending on the overall system load. In a six PSU conguration, a minimum of two power supply units are always turned on.
Since an enclosure in the Power Supply Redundancy conguration always has an extra PSU engaged, the enclosure can withstand the
loss of one online PSU. The enclosure can also 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 conguration, all power supplies are engaged when the chassis is turned on. Power utilization is monitored, and if
system conguration and power utilization allows, PSUs are moved to the Standby state. The Online status of PSUs in a grid mirrors
that of the other grid. Hence, the enclosure can sustain the loss of power to an entire grid without interruption of power to the
enclosure.
An increase in power demand in the Grid Redundancy conguration causes the engagement of PSUs from the Standby state. This
maintains the mirrored conguration needed for dual-grid redundancy.
NOTE: With DPSE Enabled, the Standby PSUs are brought Online to reclaim power if power demand increases in all three
Power Redundancy policy modes.
Default Redundancy Conguration
The default redundancy conguration for a chassis depends on the number of PSUs it contains, as shown in the following table.
Table 45. Default Redundancy Conguration
PSU Conguration Default Redundancy Policy Default Dynamic PSU Engagement Setting
Six PSUs Grid Redundancy Disabled
Three PSUs No Redundancy Disabled
Grid Redundancy
In Grid Redundancy mode with six PSUs, all six PSUs are active. The three PSUs on the left must connect to one input power grid, while
the three PSUs on the right connect to another power grid.
CAUTION
: To avoid a system failure and for Grid Redundancy to work eectively, there must be a balanced set of PSU properly
cabled to separate grids.
If one grid fails, the PSUs on the functioning grid take over without interruption to 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 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, are utilized
to improve power eciency of the system if DPSE is enabled. Subsequent failures after loss of redundancy may cause the servers in the
chassis to power down.
Managing and Monitoring Power
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