When grid power goes out, all servers in a rack lose power immediately. The server administrator confirms the servers have dual power supplies, which are connected to separate PDUs. Each of the PDUs…

Incorrect voltage settings would cause equipment damage or failure to power on initially, not a sudden loss of power coinciding precisely with a grid outage.

PDU circuit breakers can trip simultaneously during a power transient or surge that accompanies grid power loss, cutting the electrical path from the UPS devices to the servers. Even though UPS batteries may be charged and functioning, a tripped circuit on the PDU prevents power from reaching the server power supplies. This is the most likely single-event explanation for immediate, complete power loss across all servers despite the redundant UPS design.

Simultaneous failure of all server power supplies at the exact moment of a grid outage is statistically improbable and does not explain why both independent UPS devices provided no protection.

Discharged UPS batteries would cause power loss as stored energy depleted, but the scenario describes immediate power loss rather than a gradual fade, making battery discharge a less likely cause than a tripped circuit.