RCDD · Question #283
Within a data center, if you have a system which includes one extra unit, in addition to the minimum required to satisfy the base need, and where the failure of this unit will NOT disrupt…
The correct answer is B. N+1. N+1 redundancy adds exactly one extra unit beyond the minimum required, so the failure of that single spare unit does not disrupt operations because the base requirement N is still fully satisfied.
Question
Within a data center, if you have a system which includes one extra unit, in addition to the minimum required to satisfy the base need, and where the failure of this unit will NOT disrupt operations, what level of redundancy would this represent?
Options
- AN
- BN+1
- CN+2
- D2N
- E2(N+1)
How the community answered
(27 responses)- A7% (2)
- B74% (20)
- C11% (3)
- D4% (1)
- E4% (1)
Why each option
N+1 redundancy adds exactly one extra unit beyond the minimum required, so the failure of that single spare unit does not disrupt operations because the base requirement N is still fully satisfied.
N represents only the exact minimum capacity required with zero redundancy, meaning any single failure will directly disrupt operations.
In N+1 redundancy, N represents the minimum number of units needed to meet system demand, and the single additional unit serves as a hot spare or load-sharing component. Because the N base units can independently sustain full operation, losing the one extra unit causes no service disruption. This model is widely used for UPS modules, cooling units, and power supplies in data centers where some redundancy is required without full duplication.
N+2 provides two extra units beyond the minimum, tolerating two simultaneous failures without disruption, which exceeds the single-extra-unit scenario described.
2N provides a fully duplicated system twice the base capacity, which is a complete mirror rather than a single spare unit.
2(N+1) doubles the entire N+1 configuration, representing the highest tier of redundancy far beyond adding one extra unit.
Concept tested: N+1 single-spare redundancy model in data centers
Source: https://uptimeinstitute.com/tier-certification/tier-standards
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