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# Calculating Performance Scaling on an Existing System

Use Table 15 as a worksheet for calculating the performance scaling numbers of an existing SBRC system.

Table 15: Worksheet for Calculating Performance Scaling

Category

Front End 1

Front End 2

Front End 3

Front End 4

Total

Before you start the test, you must gather the historical information of the SBRC system from the Statistics page in Web GUI.

1. Peak accepts/s.

2. Peak starts/s.

3. Peak stops/s.

4. Interims per start.

(Divide the interim requests by total starts.)

5. Challenges per accept.

(Divide challenges by total accepts.)

Clear the results from the Web GUI and examine the system load at high usage for a defined period (5 minutes). This should not significantly impact the system performance.

6. Average accepts/s.

7. Average starts/s.

8. Average stops/s.

9. Interims per start.

10. Challenges per accept.

View the system statistics during the trial period.

11. Run prstat with average load during test.

12. Run prstat –L to view the highest thread utilization.

13. Run sar 300 1 to calculate the usr percentage.

14. Run sar to calculate the sys percentage.

15. Run iostat 300 1 for I/O utilization, in kps.

16. Run psrinfo to determine the virtual CPU count.

17. One CPU as a percent of the system.

(Divide 100 by the value of #16.)

Peak scaling is calculated by the result of #17 (assuming ratios of #4 and #5 are approximately equal to #9 and #10, respectively.)

18. Calculate the overall CPU utilization at peak.

(Divide the value of #11 by the value of #7 and multiply the result with the value of #2.)

If the overall CPU utilization (result of #18) is nearing 90 percent, then the system is presently constrained by the CPU utilization.

19. Calculate the highest thread utilization at peak.

(Divide the value of #12 by the value of #7 and multiply the result with the value of #2.)

If the highest thread utilization (result of #19) at peak is closer to the result of #17, then the system is presently constrained by the single-core CPU speed.

20. Calculate sar at peak.

(Add the values of #13 and #14, divide by the value of #7, and multiply by the value of #2.)

If the result of #20 is nearing 90 percent, then the system is constrained by CPU utilization. If this trend continues and exceeds 90 percent, then the system will run out of CPU resources.

The result of #20 should be similar to the result of #18.

21. Calculate iostat kps at peak.

(Divide the result of #15 by the result of #7 and multiply it by the result of #2.)

If the result of #21 is nearing 60 percent of the rated speed of the drive, then the system will soon become I/O bounded.

#### Modified: 2017-09-26 