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MTBF MTTR MTTD

MTBF - Mean Time Between Failure/Incident
MTTR - Mean Time To Repair /Response
MTTF - Mean Time to Failure
MTTD - Mean Time to Detect/Diagnose

Metrics Used in Availability Management

There are a number of measures used to assess and report the performance of a service or component in respect of it being available.

Availability is defined as the ability of a service or component to perform its required function when needed. It is usually calculated as a percentage.
  
                   Availability = MTBF/(MTBF+MTTR)

 Reliability is a measure of how long a service or component can perform its required function without interruption. It is calculated using the metrics Mean Time between System Incidents & Mean Time to Restore Services.

Maintainability is a measure of how quickly a service or component can be restored to its working state after a failure.

Note: Availability, reliability and maintainability measures all need to include a time interval, typically hours.

Serviceability is a measure of a third-party provider’s ability to meet their contracted support commitments in terms of availability, reliability and maintainability.

 Failure : Any system that cannot meet minimum performance or availability requirements can be considered as failed.

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