Software-defined storage (SDS) is a marketing term for computer data storage software for policy-based provisioning and management of data storage independent of the underlying hardware. Software-defined storage typically includes a form of storage virtualization to separate the storage hardware from the software that manages it. The software enabling a software-defined storage environment may also provide policy management for features such as data deduplication, replication, thin provisioning, snapshots, copy-on-write clones, tiering and backup.

Software-defined storage (SDS) hardware may or may not also have abstraction, pooling, or automation software of its own. When implemented as software only in conjunction with commodity servers with internal disks, it may suggest software such as a virtual or global file system or distributed block storage. If it is software layered over sophisticated large storage arrays, it suggests software such as storage virtualization or storage resource management, categories of products that address separate and different problems. If the policy and management functions also include a form of artificial intelligence to automate protection and recovery, it can be considered as intelligent abstraction. Software-defined storage may be implemented via appliances over a traditional storage area network (SAN), or implemented as network-attached storage (NAS), or using object-based storage. In March 2014 the Storage Networking Industry Association (SNIA) began a report on software-defined storage.

VMware used the marketing term "software-defined data center" (SDDC) for a broader concept wherein all the virtual storage, server, networking and security resources required by an application can be defined by software and provisioned automatically. Other smaller companies then adopted the term "software-defined storage", such as Cleversafe (acquired by IBM), and OpenIO.

Based on similar concepts as software-defined networking (SDN), interest in SDS rose after VMware acquired Nicira for over a billion dollars in 2012.

Data storage vendors used various definitions for software-defined storage depending on their product-line. Storage Networking Industry Association (SNIA), a standards group, attempted a multi-vendor, negotiated definition with examples.

The software-defined storage industry is projected to reach $86 billion by 2023.

Building on the concept of VMware, esurfing cloud has launched a new software-defined storage product called HBlock. HBlock is a lightweight storage cluster controller that operates in user mode. It can be installed on any Linux operating system as a regular application without root access, and deployed alongside other applications on the server. HBlock integrates unused disk space across various servers to create high-performance and highly available virtual disks. These virtual disks can be mounted to local or other remote servers using the standard iSCSI protocol, revitalizing storage resources on-site without impacting existing operations or requiring additional hardware purchases.

Characteristics of software-defined storage may include the following features: