Dual Power Supplies on Different Sources: Fault Tolerance vs Redundancy

Server Hardware & High Availability

Which of the following concepts is in use when dual power supplies are connected to different power sources?

Fault tolerance Source Reference Answer
Active-passive
Component redundancy
Heartbeat
Link aggregation

Community Votes

62%

38%

62% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

The exam tests if you recognize that redundancy alone (duplicate components) does not guarantee availability if a single point of failure remains; fault tolerance requires eliminating common cause failures like shared power grids.

This question tests the distinction between component redundancy and fault tolerance in server infrastructure. The community consensus confirms that connecting power supplies to different external sources elevates the concept from simple redundancy to full fault tolerance.

Candidates often select Component Redundancy because they focus only on the presence of two physical power supply units, ignoring the critical detail that they are connected to separate power sources which eliminates a systemic risk.

Community Discussion (5 comments)

cj207800 👍 1 Selected: A

Fault tolerance is a broader concept that encompasses various strategies to ensure system reliability and availability, including component redundancy. In the case of dual power supplies connected to different power sources, the primary goal is to create a fault-tolerant system that can continue operating even if one power source fails. Component redundancy is indeed a part of this setup, as there are two power supply units. However, the key aspect here is not just the redundancy of components, but the ability of the system to maintain operation in the face of a power source failure. This ability to continue functioning despite a fault is the essence of fault tolerance

Stache 👍 1 Selected: C

This question sucks so hard. Going with (C). Per the CompTIA Server+ Student Guide: Component redundancy is within the server or network. For example, a single server may have multiple NICs or multiple power supplies. * With that said, the above was all under the Fault Tolerance section of the lesson, but since it's so clearly described I'm going with "Component Redundancy". Again, what absolute disingenuous phrasing and options from CompTIA.

Ronn_Burgandy 👍 2 Selected: A

The most correct answer is A. Fault Tolerance would encompass both the different power supplies AND the different power sources. C. would only include the different power supplies.

SecNoob27639 👍 2 Selected: A

Different Power Sources is the key here. Dual Power Supplies connected to the same power source is redundancy for if one power supply fails. Dual Power Supplies connected to DIFFERENT power sources, as detailed in the question, is redundancy for if the power source itself fails. This would ensure that if one power source (like main power from the Grid) fails/goes out, the secondary supply connected to a different power source (like a building generator) would allow continued operation.

tomf021959 👍 2 Selected: C

"FT ensures minimal and core business operations stay online, whereas redundancy is concerned with duplication of hardware and software" https://www.liquidweb.com/kb/high-availability-vs-fault-tolerance/

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Expert Analysis

Why the Answer Is Correct

Fault tolerance is defined as the ability of a system to continue operating without interruption when one or more of its components fail. By connecting dual power supplies to entirely different power sources (e.g., separate UPS units or electrical grids), the system mitigates the risk of a total power loss due to a single source failure. This configuration ensures that the failure of one power path does not impact the other, thereby achieving fault tolerance.

Why the Other Options Are Wrong

Component redundancy refers merely to having duplicate hardware components, such as two power supplies, but it does not inherently address how they are powered. If both redundant supplies were plugged into the same circuit breaker or PDU, a failure in that upstream source would still take down the server, meaning it lacks fault tolerance for power loss. Active-passive describes a clustering mode where one node stands by, which is irrelevant to internal server power architecture. Heartbeat signals are used for cluster health monitoring, and link aggregation combines network interfaces, neither of which relates to power supply configurations.

Community Comment Notes

Commenters highlight that 'Different Power Sources' is the key discriminator that pushes the answer from redundancy to fault tolerance. One user notes that while component redundancy is present, fault tolerance is the broader, more accurate concept encompassing the entire resilient design. Another commenter references official study guides that place this specific setup under the Fault Tolerance section, reinforcing that redundancy is a tactic used to achieve the goal of fault tolerance.

Official Reference

Array

Exam Strategy

When analyzing HA/DR questions, always look for 'single points of failure.' If the solution includes duplicate components AND removes shared dependencies (like separate power circuits, RAID controllers, or network paths), the answer is likely Fault Tolerance rather than just Redundancy.

Related Analysis

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