UGC NET CSE | July 2018 | Part 2 | Question: 14

Question

A software system crashed 20 times in the year 2017 and for each crash, it took 2 minutes to restart. Approximately, what was the software availability in that year?

• A. 96.9924%
• B. 97.9924%
• C. 98.9924%
• D. 99.9924%

Comments

Software availability is the probability that a program is operating according to
requirements at a given point in time and is defined as
Availability =MTTF / (MTTF+MTTR)

 here  MTTF=365*1440/20=26280  and MTTR=2  so ans =26280/26282 =99.9924 %

Answer 1

Software availability is the probability that a program is operating at a given point in time

Given time period 365 days  each day has 1440 minutes

so total time in minutes =365x1440=525600

Non  working time =20x2 =40 minutes (20 times failed each time it took 2 min to restart)

Software availability = 525560 / 525600 = .999924 or 99.9924 %

Hence option 4 is right ans

Answer 2

I think 4 is the answer

Since S/W crashed 20 times and each crash take 2 min

so waste time in crash=20*2=40 min

Now total time in year in min=365*24*60

so % crash time in that year=(40/365*24*60)*100

so availability time that year = 1-(40/365*24*60)*100

                                             =99.9924%

Answer 3

Option D. 99.9924%

Availability =  $\frac{MTBF}{MTBF + MTTR}$ 
MTBF = Mean time between failure
MTTR = Mean time to repair