A more civilized iostat, with 100x more precision, and exportable to CSV format.
$ cstat
elapsed busy% sys% user% nice% idle%
1 2.707 1.140 1.567 0.000 97.293
2 1.702 0.567 1.135 0.000 98.298
3 1.994 0.997 0.997 0.000 98.006
4 1.569 0.571 0.999 0.000 98.431
5 6.695 1.994 4.701 0.000 93.305
6 6.553 2.707 3.846 0.000 93.447
Just show the busy column, polling every 5 seconds for up to 5 minutes:
$ cstat --poll 5s --for 5m --busy --header=false
10.734
7.532
9.400
8.460