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ITIL · Question #112

Which one of the following is the BEST definition of reliability?

The correct answer is C. How long a service or configuration item (CI) can perform its function without failing. Reliability is defined as the ability of a service or CI to perform its required function without interruption over a period of time, often measured as Mean Time Between Failures (MTBF).

Generic concepts and definitions

Question

Which one of the following is the BEST definition of reliability?

Options

  • AThe availability of a service or component
  • BThe level of risk that affects a service or process
  • CHow long a service or configuration item (CI) can perform its function without failing
  • DHow quickly a service or component can be restored to normal working order

How the community answered

(63 responses)
  • A
    2% (1)
  • B
    5% (3)
  • C
    90% (57)
  • D
    3% (2)

Why each option

Reliability is defined as the ability of a service or CI to perform its required function without interruption over a period of time, often measured as Mean Time Between Failures (MTBF).

AThe availability of a service or component

Availability measures the proportion of agreed service time a service is actually operational, which incorporates both reliability and recoverability rather than defining reliability alone.

BThe level of risk that affects a service or process

The level of risk affecting a service or process is the definition of risk exposure, not reliability.

CHow long a service or configuration item (CI) can perform its function without failingCorrect

Reliability specifically measures the duration a service or configuration item can continuously perform its intended function without experiencing a failure. This maps directly to the ITIL definition and the industry-standard metric MTBF, distinguishing it from availability (which includes recovery time) and maintainability (which measures restoration speed).

DHow quickly a service or component can be restored to normal working order

How quickly a service or component is restored to working order describes maintainability or recoverability, specifically measured by Mean Time To Restore (MTTR), not reliability.

Concept tested: ITIL definition of reliability versus related concepts

Source: https://www.axelos.com/certifications/itil-service-management/itil-4-foundation

Topics

#Reliability#availability#MTBF#service continuity

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