Disk Performance

Use iostat to get the performance data
# iostat -x

Device:       rrqm/s   wrqm/s   r/s   w/s       rsec/s   wsec/s   avgrq-sz avgqu-sz   await  svctm  %util
sda               0.48          2.76     1.90  0.92        56.44     29.40    30.53         0.01        4.48       2.46      0.69

Work out the queue length
requests * average wait time / 1000 = queue length
((1.90+0.92) * 4.48) / 1000 = 0.01

Calculate the throughput
reads and writes * sector size
(56.44+29.40) * 512 / 1024 = 43Ki

Calculate utilization
requests * service time / 1000 * 100 = utilization
(1.90+0.92) * 2.46 / 1000 * 100 = 0.69 

Determine peak arrival rate
1/service time * 1000
(1/2.46 )*1000 = 406.5