While customizing the memory system design or picking the most fitting design for applications is very critical, many software vendors refrain from releasing their software for several reasons. First, many applications are proprietary, hence releasing them to hardware architects or vendors is not desired. Second, applications such as defense and nuclear simulations are very sensitive, hence accessing them is very restricted. Nonetheless, customizing the hardware for such applications is still important and highly desired. Workload cloning is the technique of generating synthetic clones from the original workload. The clones mimic the memory access behavior of the original workloads, hence enable exploring the design space with high level of accuracy. In this article, we survey the state-of-art cloning techniques of the memory access behavior and their uses.