What is software-defined storage (SDS)?

Effectively, SDS abstracts available storage resources within an organization’s broad storage environment across various types of storage devices and systems. While traditional network-attached storage (NAS) or storage area network (SAN) systems are often dependent on proprietary hardware or vendor-specific software, SDS solutions generally use commodity hardware, such as any industry-standard or x86 server, and can unite otherwise incompatible systems.

Through abstraction, SDS allows for policy-based provisioning and dynamic storage resource management, independent of the unique storage hardware being used. SDS uses virtualization to create a unified pool of storage resources that can be dynamically allocated either through automation or manually through a software-enabled dashboard interface.

Typically, traditional data storage infrastructure is composed of various pieces of storage hardware, each managed by proprietary software. This approach often results in a rigid structure bound to inflexible vendor or manufacturer systems, making maintenance, data migration and expansion more difficult. Data fragmentation and reduced data visibility also become greater issues as traditional storage techniques contribute to increased data silos and system complexity.

SDS frees organizations from relying on proprietary infrastructure and offers the freedom to select the vendors and hardware best suited for their needs. Abstracted storage also offers better flexibility, efficiency and faster scalability, with the ability to scale out specific storage resources independent of other data center components, such as compute and networking resources.

As a category, software-defined storage (SDS) comprises many individual technologies that separate storage management and resources from the underlying hardware, each with its own task-dependent use cases. Some common forms of SDS include:

• Software-defined storage appliances: Virtual appliances replicating hardware applications through software running on standard services or virtual machines (VMs), providing typical storage services like data duplication, data replication and thin provisioning.
• Virtual SAN (VSAN): A virtual storage area network (SAN) aggregates local storage from multiple clustered servers to create a shared storage pool, enabling organizations to use direct-attached storage (DAS) in a virtualized environment without traditional shared storage arrays. 
• Scale-out file systems: A type of distributed file system designed to scale out horizontally through the addition of more nodes to the cluster, boosting storage capacity and performance over multiple servers.
• Software-defined object storage (SDOS): Specialized SDS systems designed for an object storage approach that treats individual pieces of data as discrete objects as opposed to a file hierarchy or segmented data blocks.
• Software-defined storage for block storage: Another type of specialized SDS that is specifically designed for block storage, with features like snapshots, thin provisioning and data replication.
• Software-defined storage for storage area networks (SAN): SDS designed to enable centralized storage management and virtualization of SAN resources.
• Software-defined storage for cloud: SDS designed specifically for cloud storage environments, offering organizations flexible and scalable cloud-based storage by abstracting underlying physical hardware.
• Hyperconverged storage: Hyperconverged infrastructure (HCI) solutions use virtualization to not just abstract storage, but entire data centers, including compute and networking components. Just as HCI uses virtualization to replace networking hardware with software-defined networking (SDN), HCI also uses SDS to manage storage resources for efficient dynamic resource allocation.

Software-defined storage (SDS) achieves the process of abstracting storage through a software layer, such as a hypervisor. This software functions as a central supervisory system that is capable of effectively managing, virtualizing and controlling all available storage resources across different types of storage, including SAN, SSD and more. Additionally, a storage hypervisor increases the availability, speed and use of total resources over disparate storage systems with improved flexibility and efficiency, while providing valuable services like automated provisioning, snapshots, data duplication and replication.

As a virtual layer, a storage hypervisor can provide centralized and streamlined storage access, greatly simplifying IT operations and facilitating smooth integrations of dissimilar or incompatible storage models suitable for diverse applications.

Software-defined storage (SDS) solutions are composed of several key features.

In addition to improved efficiency and performance, SDS offers several compelling benefits to organizations.

SDS is a cost-effective method for maximizing the value of existing storage resources and improving the capacity of owned storage without purchasing new hardware. By freeing storage resources from the underlying hardware, SDS also allows organizations to use low-cost storage alternatives instead of expensive proprietary hardware.

Because virtualized storage is not dependent on any proprietary hardware or software limitations, SDS is an effective way to free organizations from vendor lock-in, allowing for greater flexibility in hardware selection.

SDS can significantly streamline many storage-management-related tasks, reducing IT expenses by either automating or simplifying complicated workloads related to storage provisioning, monitoring and troubleshooting.

SDS is well suited for operations seeking to not just scale up, but also scale out. SDS supports linear scalability by enabling organizations to easily add additional storage nodes—including SAN disks, SSD and others—without requiring the addition of extraneous compute and network nodes.

Software-defined storage (SDS) is a valuable solution for organizations looking to optimize their storage architecture either for efficiency, compatibility or flexibility, and it can prove an even greater value for many specific use-cases common in today’s digital landscape, including the following.