Checking VM and datastore performance issues with ESXTOP

SSH into the ESXI host and launch ESXTOP:

esxtop

Hit 'v' on the keyboard to display the VM view.

Now hit 'f' and ensure that the 'F', 'G' and 'H' are selected so that the latency stats are displayed.

Hit enter and review LAT/rd and LAT/wr stats.

As a rough baseline typically anything above 20ms is considered poor performance, anything below this should be acceptable in most cases.

You can also view the overall performance of a whole datastore by pressing the 'u' key (and ensuring the appropriate latency fields are included.)

again as a guideline anything above 20ms should be considered poor performance.