Linux iostat and little's law

Linux iostat and little's law first read iostat output: [plain] root @ cnFOL :~ # Iostat-xm 60 10 Linux 3.2.0-54-generic-pae (cnFOL) August 29 _ i686 _ (1 CPU) avg-cpu: % user % nice % system % iowait % steal % idle 0.18 0.06 0.08 0.23 Device: rrqm/s wrqm/s r/s w/s RMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm % util sda 0.13 0.79 0.30 0.30 0.00 0.00 28.74 0.02 26.44 5.89 46.42 4.31 0.26 avg-cpu: % user % nice % system % iowait % steal % idle 0.07 0.00 0.07 0.13 Device: rrqm/s wrqm/s r/s w/s RMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm % util sda 0.00 0.20 0.00 0.20 0.00 0.00 16.00 0.00 6.00 0.00 6.00 6.00 0.12 parameter comment r/s: read operations per second w/s: write operations per second await: average response time for read/write operations svctm: Average service time for read/write operations avgqu-sz: average queue length % util: average utilization Cotel rule: average queue length = average arrival rate * average response time * 0.001 Calculated as follows: avgqu-sz = (r/s + w/s) * await * 0.001 utilization rule: average utilization = average arrival rate * Average service time * 0.001 calculation: % util = (r/s + w/s) * svctm * 0.001