Hardware appliances have dominated the enterprise data storage landscape for decades, but storage is not immune from the software-defined transformation taking place in data centers. With momentum building for converged server and storage architectures, it is the right time for infrastructure and operations (I&O) professionals to evaluate software-only storage offerings running on commodity hardware. This market overview delves into the emergence of software as an alternative to hardware appliances and gives a detailed overview of 15 vendors' software-only storage offerings.