Operating Systems

1. Calculate the reliability of a hard disk drive with an MTBF of 2,499 hours during the last 40 hours of this month. Assume e = 2.71828 and use the formula: reliability(t) = e -(1/MTBF)(t)

2. Review the system with one CPU and four drives below:

– CPU W = 4 ms (the average time to execute 1,000 instructions)

– Drive A = 45 ms (average data access speed)

– Drive B = 3 ms (average data access speed)

– Drive C = 17 ms (average data access speed)

– Drive D = 10 ms (average data access speed)

Calculate I/O access speed using this CPU and each of the four disk drives as they evaluate the following track requests in this order: 0, 31, 20, 15, 20, 31, 15. Then in each case, calculate the access speeds after the track requests are reordered and rank the four disk drives before and after reordering.