What Is Software‑Defined Storage and Why It’s Shaping the Future of IT

1. What Is Software‑Defined Storage (SDS)

Software is the interface between users and hardware; traditionally many functions were hard‑wired into hardware, creating a "hardware‑defined" model. As demand for flexible, automated services grows, software‑defined approaches decouple hardware capabilities and expose them via APIs or services.

Software is the interface between users and hardware.

In IT, the first software‑defined concept was Software‑Defined Networking (SDN), which separates the control plane from the data plane to enable programmable network traffic. VMware later introduced Software‑Defined Data Center (SDDC) and defined Software‑Defined Storage (SDS) as one of its five pillars.

VMware describes SDS as a solution that abstracts hardware, pools resources, and provides them through a user‑friendly UI or API, allowing seamless scale‑up or scale‑out without additional workload.

Infrastructure services are aggregated with policy‑based automation and monitoring.

APIs and connectors enable seamless extension to private, hybrid, and public clouds.

Key concepts to remember are abstraction, pooling, and automation.

2. SDS Classification

SDS encompasses many sub‑areas such as storage virtualization and Server SAN. Understanding the distinction between the control plane (automation) and the data plane (hardware‑software decoupling and pooling) is essential.

Control Plane

Notable solutions include:

VMware SPBM (Storage Policy Based Management)

OpenStack Cinder

EMC ViPR

ProphetStor Federator

FalconStor Freestor

Data Plane

Based on commodity hardware, it includes virtual storage appliances (VSA), physical storage appliances, and hyper‑converged infrastructure (HCI) such as VMware VSAN, Nutanix, and Huawei FusionStorage.

Traditional external SAN/NAS products (e.g., EMC VNX, NetApp FAS, Huawei OceanStor) are also adopting SDS features through API integration and virtualization.

Cloud/Object storage acts as a data‑plane component, exposing storage via RESTful APIs (Amazon S3, SNIA CDMI, OpenStack Swift) for VM/App consumption.

3. SDS Development: Past, Present, Future

SDS emerged to meet growing data volumes, personalization, IoT, and the rise of virtualization and cloud computing, enabling storage‑as‑a‑service with rapid provisioning, dynamic scaling, and simplified management.

Advances in CPU performance, SSD capacity, high‑speed networking, and distributed storage have made Server SAN viable. Modern SDS focuses on abstraction, pooling, and automation, with automation being the most challenging yet critical stage.

Future growth is expected from vendors that combine hypervisor/OS capabilities with SDS, such as VMware (vSphere + VSAN), Red Hat (KVM + Ceph/Gluster), and Microsoft (Hyper‑V + Storage Spaces).

4. Q&A Highlights

Q: Is VSAN an SDS implementation and a Server SAN? A: Yes.

Q: Do Huawei and other vendors offer distributed storage? A: Huawei FusionStorage and others provide distributed storage solutions.

Q: Will SDS unify existing storage devices for unified management? A: Some companies are already attempting this.

Q: Does VSAN handle hot‑cold data migration? A: It supports caching; full tiering is planned.

Q: How many VSAN customers exist? A: Over 2,000, spanning finance, telecom, government, education, and healthcare.

Q: How does SDS affect virtualization and cloud computing? A: SDS is a core component of IaaS, enabling automation and storage‑as‑service, which in turn accelerates virtualization and cloud adoption.

Q: What are the advantages of Server SAN over FC SAN? A: Server SAN offers lower latency and higher performance by placing storage close to compute.

Q: Do Server SAN nodes act as both storage and control nodes? A: Yes; each node runs a management VM (e.g., Nutanix CVM) that controls I/O for other VMs.