it depends on the kind of applications / loads you are performing, so really it's not possible to put a static value to that. best is just to test it with some

it depends on the kind of applications / loads you are performing, so really it's not possible to put a static value to that. best is just to test it with some benchmarks yourself to be sure how it impacts you. some people report losses of like 20%, others 1 or 2%...