To deal with large amounts of data while offering high availability and throughput and low latency, cloud computing systems rely on distributed, partitioned, and replicated data stores. Such cloud storage systems are complex software artifacts that are very hard to design and analyze. Formal specification and model checking should therefore be beneficial during their design and validation. In particular, I propose rewriting logic and its accompanying Maude tools as a suitable framework for formally specifying and analyzing both the correctness and the performance of cloud storage systems. This abstract of an invited talk gives a short overview of the use of rewriting logic at the University of Illinois Assured Cloud Computing center on industrial data stores such as Google’s Megastore and Facebook/Apache’s Cassandra. I also briefly summarize the experiences of the use of a different formal method for similar purposes by engineers at Amazon Web Services.