The answer is "obviously yes" since the cloud providers test all this (it is probably assumed so by people). Their conclusion is that they obviously can support the services with the promised encryption without noticeable degradation for the services. Also, obvious is that this info is not public! (Experimentally, in a cluster environment you can emulate tasks with and without encryption of data at rest and figure more or less for yourself what is the performance penalites-- it is a nice project to try!)