Question

In a server farm such as that used by Amazon or eBay, a single failure does not cause the entire system to crash. Instead, it will reduce the number of requests that can be satisfied at any one time. If a company has 10,000 computers, each with a MTTF of 35 days, and it experiences catastrophic failure only if 1/3 of the computers fail, what is the MTTF for the system? (Assume that computers are not repaired.)

Answer 1

Answer:12 days

Explanation:

Mean time to failure is given by

MTTF=$\frac{Total working hours of running}{Total no. of units}$

Let's say N is the average amount  of time system runs until $\frac{1}{3}$ computer fail

MTTF of each computer =35

35=$\frac{n\cdot 10,000}{10,000\cdot \frac{1}{3}}$

$35=N\cdot 3$

N=$\frac{35}{3}=11.667\approx 12days$