I do not know of a way in vrops to group VMs by the datastore they are on. The relationship is in vrops but for some reason it is not exposed as a metric/property against the VM object co creating a group or filter to show all the vms of datastores ending in R is not possible.
The only way i can think of it it to add a vsphere tag and add it to the Vms that are on the datastores you need to group together in vcenter. You can then create a custom group in vrops that uses the vsphere tag as its membership rule.
Your next problem will be getting the cumulative demand against an container object (the custom group) I have not done this but i think your only way is to create a super metric to sum all the CPU/memory demand and use it as a container object will only report badge metric and super metrics.
If a list of the objects within the custom group with a summery at the bottom would do then create a list view using the custom group as the filter.
I personal cant think of another way to do this and even if the above will work.
