We have a good amount of VMs in a hosted vmware environment. Our service provider offers faster speed disks for our vms.. Currently we are on the slowest SATA based SANs. I am not sure if I need to upgrade to the faster disks, but want to make sure my VMs are doing ok on the current SANs. What is the best way to monitor my disk performance? Are there any 3rd party tools for checking as well?