information Systems Hw

ISE 218: Fundamentals of Information Technology

Stony Brook University

Homework #6

Fall 2017

Assignment Due: November 13, 2017 at the start of lecture

Neatly write or type your answers to the following problems on a separate sheet of paper and submit a hard copy at the start of lecture on the due date. For any problems involving mathematical calculations you must show all work to receive full credit.

Please clearly print or type your full name and Stony Brook ID # on your paper.

Submissions that are not stapled will be docked 5 points.

1. [5 pts] Calculate the overall speedup of a system that spends 40% of its time in calculations with a processor upgrade that provides for 100% greater throughput. Give your final answer to two digits to the right of the decimal point.

2. Suppose your company has decided that it needs to make certain busy servers 30% faster. Processes in the workload spend 70% of their time using the CPU and 30% on I/O. In order to achieve an overall system speedup of 30%:

a. [5 pts] How much faster does the CPU need to be? Give your final answer to two digits to the right of the decimal point.

b. [5 pts] How much faster does the disk need to be? Give your final answer to two digits to the right of the decimal point.

3. Suppose the daytime processing load of some computing server consists of 60% CPU activity and 40% disk activity. Customers are complaining that the system is slow. After doing some research, you have learned that you can upgrade your disks for $8,000 to make them 2.5 times faster than they are currently. You have also learned that you can upgrade your CPU to make it 1.4 times faster for $5,000.

a. [10 pts] Which would you choose to yield the best performance improvement for the least amount of money? Justify your answer through appropriate application of Amdahl’s Law and a cost-benefit analysis similar to the one we did in lecture.

b. [5 pts] Which option would you choose if you don’t care about the money, but want a faster system?

c. [5 pts] What is the break-even point for the upgrades? That is, what price would we need to charge for the CPU (or the disk – change only one) so the result was the same cost per 1% increase for both?

4. Suppose a disk drive has the following characteristics:

• 6 surfaces • 16,383 tracks per surface • 63 sectors per track

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• 512 bytes/sector • Tract-to-track seek time of 8.5 milliseconds • Rotational speed of 7,200 RPM.

a. [5 pts] What is the capacity of the drive in GB? Use base-2 units of measure, i.e., 1 GB = 230 bytes.

b. [5 pts] What is the access time in ms?

5. [5 pts] Suppose you have a 2 TB database housed on a disk array that supports a transfer rate of 350 MBps and a tape drive that supports 200 GB cartridges with a transfer rate of 300 MB per second. How long will it take in minutes to back up the database?

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