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
Compare: vmstat 1
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
Can also show the memory usage, optionally include swap memory with --swap option.
$ mstat
elapsed total used free shared buffers cached available
1 32764724 4920732 4303108 175828 6925284 16615600 27238244
2 32764724 4920984 4302856 175828 6925292 16615592 27237992
3 32764724 4921476 4302352 175828 6925292 16615604 27237492
Compare: free -k