Consider an interactive system with a CPU and two disks. The following measurement data was obtained by observing the system:
Observation interval = 17 minutes
Mean think time = 12 seconds
Number of completed transactions during observation interval = 1,600
Number of completions at CPU = 1,600
Number of fast disk accesses = 32,000
Number of slow disk accesses = 12,000
CPU busy time = 1,080 seconds
Fast disk busy time = 400 seconds
Slow disk busy time = 600 seconds
Give asymptotic bounds on throughput and response time as a function of the number of terminals.
Now consider the following modifications to the system:
Move all files to the fast disk.
Replace the slow disk by a second fast disk.
Increase the CPU speed by 50% (with original disks),
Increase the CPU speed by 50% and balance the disk load across the two fast disks.
For each of these four modifications, compute and graph the effects on the original system. Explain in words the effect when the multiprogramming level, N, is small and when Nis large.