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Availability

The general formula for availability is:

Availability = [MTBF/(MTBF+MTTR)] x 100

Availability is a function of the total service time, the mean time between failure (MTBF), and the mean time to repair (MTTR).

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This KPI is most used for:
Operational Excellence

Comments

  1. Andy S.

    Can you use this general formula also for hardware? Thanks on advance

  2. tarig A.

    Dears

    please advice regarding the availability of the whole system ; i think the above availability is for a one service/link/node, so in case we have number of nodes occupied by number of links each link occupied by number of service how can i calculate the system availability.

    thanks for your swift feed back.

    Tarig Alamin

  3. Sean M.

    There are two more formulas for Service Availability, this one here relates only to a single instance of a productive unit.

    In Serial Mode:

    that is one Productive Unit (PU) after another PU the formula is:

    Service Availability = PU1 availability * PU2 availability (* PUn availability and so on)

    so 100% * 98% = 98%
    and 98% * 98% = 96.04% availability

    In Parallel mode:

    where PU1 and PU2 are linked such that one takes over should the other fail the PU Total availability needs to be calculated first:

    1 – (1-PU1 availability(original availabilty measure for single PU)))*(1-PU2 availabilty))

    so (PU1 and 2 are parallel such that PU2 takes over if PU1 fails) 1-((1-98%(PU1))*(1-98%(PU2)))=99.96%

    it is possible now to combine the serial and parallel availability calculations to create very complex Service Availabilities.

    I always draw out a diagram of how to work this out, makes life a lot easier.

    regards
    Sean

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