I have many VMs in our environment.
I use vCenter to manage VM.
If I want to know which VMs are unused or the frequency of use is not high.
How to get the data?
the better way to get report, please install Vcenter operation manager, you can pull out all the information and reports through Vcenter Operation Manager. there in the report area you can get the data's about oversized vm ideal vm's and about host as well
vCOPS is definitely the best way to get this information, it is an additional product which some people dont have or cant have.
If not for an additional tool the only way to grab this in bulk would be to use powercli and pull the information out of vCenter into a csv file or something like that. do a search and you will find plenty of powercli scripts out there relating to vm performance gathering. or you can write your own
Have a look at your cluster's performance monitor and set to "virtual machine operations" in advanced chart options.
Edit: Sorry, you can't get information about specific VMs in that view.
that is not free tho
vCOPS is not free, but it is a very good product for monitoring, data analysis, reporting and more. And, when you have "many" VMs, it's really the only product that can easily and quickly allow you to perform all the previously mentioned operations.
PowerCLI is a free alternative, but there is quite a bit of manual work involved.