Ac Redundancy Policy; Power Supply Redundancy Policy; Dynamic Power Supply Engagement - Dell PowerEdge VRTX User Manual

AC Redundancy Policy

The purpose of the AC redundancy policy is to enable a modular enclosure system to operate in a mode in which it can
tolerate AC power failures. These failures may originate in the AC power grid, the cabling and delivery, or a PSU itself.
When you configure a system for AC redundancy, the PSUs are divided into grids: PSUs in slots 1 and 2 are in the first
grid while PSUs in slots 3 and 4 are in the second grid. CMC manages power so that if there is a failure of either grid, the
system continues to operate without any degradation. AC redundancy also tolerates failures of individual PSUs.
NOTE: One role of AC redundancy is to provide seamless server operation despite failure of a whole power grid,
but the most power is available to maintain AC redundancy when the capacities of the two grids are approximately
equal.
NOTE: AC redundancy is only met when the load requirements do not exceed the capacity of the weakest power
grid.
AC Redundancy Levels
One PSU in each grid is the minimum configuration necessary for use as AC redundant. Additional configurations are
possible with every combination that has at least one PSU in each grid. However, to make the maximum power available
for use, the total power of the PSUs in each leg should be as close to equal as practical. The upper limit of power while
maintaining AC redundancy is the power available on the weakest of the two grids.
If a CMC is unable to maintain AC redundancy, an e-mail and/or SNMP alert is sent to administrators, if the Redundancy
Lost event is configured for alerting.
In the event of a single PSU not functioning in this configuration, the remaining PSUs in the problematic grid are marked
as online. In this state, any remaining PSUs can stop functioning without interrupting operation of the system. If a PSU
stops functioning, the chassis health is marked non-critical. If the smaller grid cannot support the total chassis power
allocations, then AC redundancy status is reported as No, and the health of chassis is displayed as Critical.

Power Supply Redundancy Policy

The power supply redundancy policy is useful when redundant power grids are not available, but you may want to be
protected against a single PSU failure bringing down your servers in a modular enclosure. The highest capacity PSU is
kept in online reserve for this purpose. This forms a Power Supply redundancy pool. The figure below illustrates power
supply redundancy mode.
PSUs beyond those required for power and redundancy are still available and is added to the pool in the event of a
failure.
Unlike AC redundancy, when power supply redundancy is selected, CMC does not require the PSU units to be present in
any specific PSU slot positions.
NOTE: Dynamic Power Supply Engagement (DPSE) allows PSUs to be placed in standby. The standby state
indicates a physical state of PSUs that are not supplying power. When you enable DPSE, the extra PSUs may be
placed in Standby mode to increase efficiency and save power.

Dynamic Power Supply Engagement

By default, Dynamic Power Supply Engagement (DPSE) mode is disabled. DPSE saves power by optimizing the power
efficiency of the PSUs that supply power to the chassis. This also results in 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.
146