3. As the CIO of a local bank, you run a datacenter consisting of a large mainframe

computer to support the network of branches and online banking. The CIO is exploring

replacing the old mainframe computer and you have been tasked to carry out a

performance study to evaluate different alternatives for replacing the existing machine

with:

i. a newer mainframe computer

ii. a cheaper computer with n homogeneous processors with one job queue

iii. three cheaper computers with n homogeneous processors divided equally among three

physical machines and each with one queue, i.e., divide the n processors in (ii) into

three separate computers, with 3 separate job queues.

Assume that the current workload and service rate of the mainframe are /2 and /2

transactions per second respectively. The CIO would like to provide capacity for doubling

of the workload and service rate to and respectively. All the three alternatives have

the same total service rates. For simplicity, you can assume that both workload and service

rate are exponentially distributed. The above are the only information and data provided

by the CIO. If you need additional assumption, data, etc, use your discretion and justify.

The CIO would like to know the following:

a. How would you model the current and the alternative systems using Markov models?

Explain your answers. [3 marks]

b. What is your recommendation? Justify your answers.

{Hint: Derive the response time and throughput for all systems and tabulate the

answers using a table. Compare the performance of the current system with the

different alternatives.} [4 marks]

c. The CIO are concerned that (i) peak workload could be 5 times the average and (ii)

variation of transaction size could be large. (iii) The CIO prefers to provide better user

response time over higher throughput. How would these considerations impact your

recommendation? [3 marks]