A server is configured in a 1+1 power configuration with both PSUs connected to a single PDU. Which redundancy options does this configuration supply?

Question

Options

• APSU redundancy only
• BPSU redundancy and PDU redundancy
• CNo redundancy unless each PSU is connected to a separate PDU
• DPSU redundancy and Grid redundancy

• A
  67% (31)
• B
  4% (2)
• C
  20% (9)
• D
  9% (4)

Explanation

Option A is correct because a 1+1 configuration provides PSU redundancy only - if one power supply fails, the other takes over, keeping the server running. However, since both PSUs feed from the same PDU, a PDU failure kills power to both PSUs simultaneously, meaning there is no PDU redundancy.

Why the distractors are wrong:

• B is wrong because PDU redundancy requires each PSU to connect to a separate PDU; a single shared PDU is a single point of failure.
• C is wrong because PSU redundancy does exist even with one PDU - the 1+1 setup handles PSU-level failures just fine; it's only PDU-level failures that aren't covered.
• D is wrong because grid redundancy requires two independent power feeds (e.g., from separate utility sources or UPS systems), which is a completely different layer not addressed here.

Memory tip: Think in layers - PSU protects against unit failure, PDU protects against distribution failure, and grid protects against source failure. Each layer needs its own redundant path; sharing a PDU collapses the PSU and PDU layers into one point of failure.

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