An administrator is troubleshooting a failure in the datacenter in which a server shut down/powered off when utility power was lost. The server had redundant power supplies. Which of the following is the most likely cause of this failure?

• A. Both power supplies were faulty
• B. One power supply was connected to a UPS
• C. Both power supplies were connected to the same power feed
• D. Server reached thermal shutdown

Answer: (C)

The most likely cause of the server's shutdown during a utility power loss is that both power supplies were connected to the same power feed. In a redundant power supply configuration, having the power supplies connected to separate power feeds ensures that if one feed fails (like in the case of a utility power outage), the other feed can continue to supply power to the server.

When both power supplies are on the same power feed, they are both subject to the same electrical conditions. Therefore, if that feed loses power, neither supply will function, leading to the complete shutdown of the server. This design flaw undermines the redundancy that power supplies are meant to provide, ultimately resulting in the failure experienced.

The other scenarios, such as both power supplies being faulty, one supply being connected to a UPS, or the server reaching thermal shutdown, do not explain the complete power loss that occurred when utility power was lost. If one supply were connected to a UPS, it should have maintained power during the outage. The thermal shutdown situation would typically indicate overheating, not a direct result of power loss.