Reflecting wrong processor utilization

[rajankur6494]

Hi Team,

I am working on model where there are 2 processors. When one is getting breakdown, it is stopping another processor and breakdown clock is resetting for both the processors. I am also gathering the breakdown cause, start time and end time. Based on this data, processing/utilization should be 83.7% but it is showing as 80.6%.

Could you help me to understand the reason behind 80.6%.

Please find the model attached.

[moehlmann_fe]

You are generating two uniformly distributed random numbers between 5 and 15 and use the smaller one. This is the same as generating a single value from a triangular distribution with min = 5, max = 15 and mode = 5. This gives an expected value of (min + mode + max)/3 = 25/3. So the uptime ratio should be (25/3) / (31/3) = 25/31 = 0.8065... 

Which is very close to the result the simulation is showing, so it seems valid to me.

[rajankur6494]

Hi @moehlmann_fe 

Thanks for your quick response!

I am capturing data for the breakdowns happening on processors. Based on this data, I am calculating the MTBF and MTTR and using the formula MTBF/(MTBF+MTTR) to calculate the reliability which coming as 83.7%.

Could you help me to know the reason of this difference?

[moehlmann_fe · Accepted solution]

It looks like you use the difference between the start times as MTBF. But that would then include the repair times, when it should only count the up time. MTBF is the time between start time and last end time.