## Availability problems

Data Centre Infrastructure
1. Calculate the reliability, $R$, of a system at time $t=\text{}20\text{}\phantom{\rule{0.3em}{0ex}}\text{}\mathrm{days}\text{}$ assuming that it experiences 0.1 failures per day.
2. A system has 5 failures over the course of a year. Calculate the MTBF in days.
3. A system has an MTBF of 150 days. How many faults may be expected over the course of two years.
4. Calculate the inherent availability, ${A}_{i}$, of a system with a mean time between failure of 120 days and a mean time to repair of 12 hours.