5.9 Exercises

1. Select from published literature or from product specification manuals two specific performance monitors. Briefly describe the two products and make a comprehensive list of the measurements provided by each monitor. Considering that the goal is to obtain input parameters for a performance model, discuss the positive and negative points of each of the two tools selected.

2. The MS Excel workbook Ch05-Ex-MPG.xls contains a list of elapsed times for 100 transactions that are executed during a period of 60 seconds. What is the average number of transactions concurrently executed?

3. The MS Excel workbook Ch05-Ex-BW.xls contains a list of transaction CPU times and their corresponding number of I/Os. Compute the basic statistics of Fig. 5.1 and draw the Box and Whisker plot for this data set. Draw an x-y scatter plot for the data using the CPU time as the x-axis and the number of I/Os as the y-axis. Visually cluster the workload. What are the characteristics of the centroids of the clusters identified?

4. Suppose that the data in Ch05-Ex-BW.xls is obtained during a period of 15 seconds, that the CPU utilization is 35%, and that the disk utilization is 80%. Consider that each cluster found in the previous exercise corresponds to one class in a QN model. What is the overall throughput of the system in tps? What is the throughput for each class in tps? Compute the service demands at the CPU and disk for each of the classes.

5. Use OpenQN.xls to solve the QN model for the previous exercise assuming that the arrival rates are equal to the class throughputs obtained in the previous exercise.

6. A performance analyst monitored a computer system with one CPU and three disks (D1, D2, and D3) for 1 hour. The system workload consists of three different types of transactions: A, B, and C. Using data collected by the software monitor and the accounting facility, the analyst obtains the following measurements: = 82%, = 28%,=20%,= 35%C0,A = 2200, C0,B = 4000, C0,C = 1000. Determine the service demands for this workload and comment. Justify any assumptions by giving their pros and cons.

7. Consider a server dedicated to transactions generated by phone orders from customers. The server consists of a single processor and two disks (A and B). Disk A contains customer data and disk B is used for paging. The analyst responsible for studying the system performance decides to build an analytic model with 3 service centers (i.e., CPU, disk A, and disk B) and 2 classes (i.e., one for order-entry transactions and one representing the system overhead). The measurement data obtained from the system monitor are: T = 900 sec, C0,trans = 1800, Ucpu = 65%, Udisk A = 20%, Udisk B = 35%, page-ins = 22,500, and page-outs = 10,000. C0,trans is the number of user transactions completed during the monitoring period. The total CPU time for user transactions recorded by the accounting system is 567 sec. Assume that:

• The CPU times required to handle a page-in and a page-out operation are 0.0015 and 0.0042 sec, respectively.

• Page-ins should be viewed as a part of the workload demand for I/O services and should be incorporated into the disk service demands. Page-out should be include in the system overhead.

Find the input parameters for the model.

8. Learn how to use the Windows XP or NT Performance Monitor. Write a program that generates a large number of I/Os to random blocks on a file. Add the %Idle Time counter for the PhysicalDisk object. This counter provides the percentage of disk idle time (i.e., 100-disk utilization). From the Control Panel select the System icon and then select the Hardware tab. Click on the Device Manager and click on the hard drive under Disk drives. Select the Policies table and locate the "Enable write caching on the disk" option. Run your program with and without caching enabled. Observe what happens to the disk utilization. Comment on the results.

9. The workload of a database server is characterized by three types of transactions: trivial, medium, and complex. The database server, which consists of one CPU and one disk, is monitored during one hour. The CPU utilization is measured at 55% and the disk utilization is measured to be 85%. Additional measurements obtained during the observation period are shown in Table 5.10.

Table 5.10. Data for Exercise 5.9

Trivial

Medium

Complex

No. of Physical I/Os

10

20

40

Total CPU Seconds

840

560

252

No. of Transactions Executed

10500

5600

2100

• Find the service demands at the CPU and disk for trivial, medium, and complex transactions.

• Assume that the arrival rates of medium and complex transactions are fixed at 1.6 tps and 0.6 tps, respectively. Using the QN solvers provided with the book, generate a graph with three average response time curves (one for each workload) as a function of the arrival rate of trivial transactions

• Repeat the item above for a situation where a new disk, identical to the existing disk, is installed in the database server in such a way that the I/O demand is balanced between the two disks.

Performance by Design: Computer Capacity Planning By Example
ISBN: 0130906735
EAN: 2147483647
Year: 2003
Pages: 166

Similar book on Amazon