Software-defined storage puts the emphasis on storage services such as deduplication or replication, instead of storage hardware. Without the constraints of a physical system, a storage resource can be used more efficiently and its administration can be simplified through automated policy-based management. For example, a storage administrator can use service levels when deciding how to provision storage and not even have to think about hardware attributes. Storage can, in effect, becomes a shared pool that runs on commodity hardware.
Software-defined storage is part of a larger industry trend that includes software-defined networking (SDN) and software-defined data centers (SDDC). As is the case with SDN, software-defined storage enables flexible management at a much more granular level through programming.
At the time of this writing, some vendors are using SDS as a synonym for storage virtualization.