guaranteed performance using storage Qos?

Hi,

OnTAP 8.3GA running on FAS8040HA

I am learning how to use storage QoS but from what i can tell, it can only throttle on storage objects. I am looking for a way to guarantee the minimum for an object instead of imposing limits. Is it possible? It seems to be true QoS should have a way to guarantee the minimum to ensure quality of service.

Thanks,