A justifiably trustworthy provisioning of cloud services can only be ensured if reliability, availability, and other dependability attributes are assessed accordingly.We present a structured approach for deriving fault injection campaigns from a failure space model of the system. Fault injection experiments are selected based on criteria of coverage, efficiency and maximality of the faultload. The resulting campaign is enacted automatically and shows the performance impact of the tested worst case non-failure scenarios.We demonstrate the feasibility of our approach with a fault tolerant deployment of an OpenStack cloud infrastructure.