The server contains six 3000-W supplies and must preserve N+2 redundancy . A 4,500-W workload requires two actively supplying PSUs because a single 3000-W supply cannot support the current load. Maintaining N+2 redundancy requires two additional PSUs to remain available beyond those required for the workload. The minimum operational complement is therefore four supplies: two supporting the power demand plus two retained for redundancy.
With six PSUs physically installed, the remaining two PSUs can be placed into standby , making option C correct.
The calculation is:
Required active capacity = ceiling(4500 W ÷ 3000 W) = 2 PSUs
Required redundancy = 2 PSUs
Minimum available PSUs = 2 + 2 = 4
Installed PSUs = 6
Eligible for standby = 6 − 4 = 2 PSUs
Power Save Mode is intended to reduce conversion losses when installed PSU capacity exceeds current demand. Cisco uses the same operating principle in UCS power management: additional supplies that are not needed to satisfy both the requested power budget and configured redundancy can be placed into power-saving operation.
Placing three supplies into standby would leave only three available supplies, violating the N+2 requirement for a workload requiring two PSUs.
Study Guide Reference: AI Infrastructure Operations and Troubleshooting — power efficiency, PSU redundancy, Power Save Mode, and UCS AI server power management.
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