vIDM is only deployed as "Global Environment", if you deploy all of the components using the easy installer. You can deploy vIDM at multiple sites actually. Or just deploy LCM and add your products separately.
This however only sort-of applies to vRA of which you can deploy 3 nodes, which would assume, that it is a active-passive cluster. However try to shut down one of the nodes and see if the product still works:)
edit: if you do not need to scale the product beyond what one vRA node is capable of, then just deploy one and replicate it somewhere, like Lalegre said. You can always expand the configuration using LCM later.