Placement is tricky. It's one of the big controversies. Some people say "you don't need to know where things are", yet if you are trying to debug why some machines always fail, its nice to know what the physical machines are. Similarly, when you want to create a cluster, you may want to say "these two close, but not same physical machine or even same PSU". However there's no easy way to test that the supplier is meeting those requests, which is why I don't like them. No testability implies you can't rely on them.