Thanks for the instructions. At the moment my VMs are on the SSD - I have two Hard Disks in my MacMini. I will install a new VM on the slow HD and let you know tomorrow.
By the way for the SSD I am seeing two entries - Write rate and Read rate. For Write rate Maximum is 83 and Average 1.649. And for Read it is 35 and 0.455. Does this make sense? This is a Samsung 840 250GB SSD.