vSphere 6 introduces a new command similar to esxtop to monitor activity on the vcenter appliance. The product seems to be in alpha status but it's already useful to see cpu, memory, disk and network activity on the vcenter itself.
1. In order to use it, first putty (ssh) into the vCenter Appliance and then type vimtop.
2. When it launches, you see a combination of cpu and memory related information. You also see the processes running on the appliance and resources used. Notice at the top you see the uptime, load averages, cpu breakdown, memory and swap related information.
3. vimtop has an "h" option for help. Type "h" again to make the help menu disappear.
4. Type "o" for network related information.
5. Type "k" to view disk related information.
6. Type "q" for quit once you are done.