iostat - Report Central Processing Unit (cpu) statistics and input/output statistics for devices and partitions.

像这样调用它会每2秒获得KB / s：

$iostat -k 2

Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
sdb               0.89         2.39         1.72     189644     136436
sda               5.42        31.79        40.89    2519836    3240543