Data read/write on device sda
Number of bytes read/write from/to the device.
CPU utilisation on device sda
Percentage of CPU time during which I/O requests were issued to the device (bandwidth utilization for the device). Device saturation occurs when this value is close to 100%.
Average service/wait time for I/O requests on device sda
The average service time (in milliseconds) for I/O requests that were issued to the device.