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What Is Software‑Defined Storage (SDS) and How It Differs from Traditional Storage

Traditional storage systems are monolithic hardware‑software bundles where the vendor provides controllers, drives, and the storage OS as a single unit. Software‑Defined Storage (SDS) takes a different approach: the storage management software is decoupled from the underlying hardware and can run on standard commodity servers. This delivers flexibility, lowers costs, and simplifies scaling. In this article, we explain what SDS is, how it compares to traditional storage arrays, explore popular solutions (Ceph, VMware vSAN), and identify the scenarios where SDS becomes the optimal choice.

1. What Is Software‑Defined Storage?

Software‑Defined Storage (SDS) is an architecture where the software that manages storage services runs on standard, commodity servers and provides a unified interface for storage resources. The core principles of SDS are:

Separation of software from hardware — the same software platform can run on servers from different vendors.
Centralised management — all storage resources (drives, nodes) are managed through a single pane of glass or API.
Automation — thin provisioning, storage policies, rebalancing, replication — all configured programmatically.
Scalability — adding new nodes linearly increases capacity and performance.

SDS does not require specialised hardware (like FC switches or HBA adapters for SAN) and can run over standard Ethernet networks, significantly reducing deployment costs.

The key difference

In traditional storage, controllers and software are a single “black box” from the vendor. With SDS, you buy servers, install storage software, and gain flexibility in hardware choice, scaling, and features. It is like the difference between buying a pre‑built server and building your own PC from components.

2. SDS vs Traditional Storage: A Comparison

Criteria	Traditional Storage (SAN/NAS)	SDS (Software‑Defined)
Hardware	Vendor‑specific, specialised	Standard commodity servers
Storage software	Embedded in controllers	Installed separately on servers
Scaling	Scale‑up (add shelves)	Scale‑out (add nodes)
Cost	High (vendor premium)	Low to moderate
Management	Vendor‑specific interfaces	API, web dashboards, cloud integration
Performance	Maximum (hardware‑optimised)	Good, but depends on servers and network
Flexibility	Limited by vendor capabilities	High — choose features for your workload

Traditional storage systems like Huawei OceanStor Dorado or Dell PowerStore remain the best choice for high‑throughput transactional systems where every microsecond counts. SDS, in turn, is ideal for cloud environments, Big Data, archives, and virtualisation with moderate latency requirements.

3. Examples of SDS Solutions

The market offers many SDS platforms, both open‑source and commercial. Here are two of the most popular:

Ceph

Ceph is an open‑source distributed storage system that provides object, file (CephFS), and block (RBD) access. Key features:

Scales to exabytes of data.
Uses erasure coding and replication for fault tolerance.
Self‑healing architecture — data is automatically redistributed when nodes fail.
Ideal for OpenStack, Kubernetes, and cloud environments.

Ceph is often deployed on rack servers with many drives, such as Dell PowerEdge R760 or Huawei FusionServer 2288H V7.

VMware vSAN

VMware vSAN is a hyperconverged SDS solution built directly into the VMware vSphere hypervisor. It pools local drives from vSphere hosts into a single shared datastore for virtual machines. Benefits:

Simple management through the familiar vCenter interface.
Supports all‑flash and hybrid configurations.
Integration with storage policies.
Optimised for virtualisation environments, especially VDI and small clusters.

vSAN requires servers from the compatibility list, but these are still standard x86 servers, e.g., Dell PowerEdge or Huawei FusionServer.

4. When to Choose SDS vs Traditional Storage

The choice depends on your priorities:

Choose traditional storage if: you need maximum performance and minimal latency (OLTP, banking, HFT); you have budget for specialised hardware; your workload is predictable and does not require frequent scaling.
Choose SDS if: you are building a cloud or hybrid infrastructure; you need flexibility in hardware choice; you want to reduce storage costs; your data grows rapidly and unpredictably.

Many enterprises use a combination: traditional storage for critical databases, and SDS for archives, backups, and development environments.

Hybrid approach

Many companies deploy SDS on the same servers that run compute clusters, creating hyperconverged infrastructure (HCI). This simplifies management and reduces infrastructure costs, especially for environments with moderate performance requirements.

5. Benefits and Challenges of SDS

Benefits of SDS:

Lower TCO — commodity servers are cheaper than specialised storage arrays.
Flexibility — you can mix servers of different generations and vendors.
Scalability — add nodes as you grow, without downtime.
API‑driven management — integration with cloud orchestrators (Kubernetes, OpenStack, Terraform).
Fault tolerance — distributed architecture with replication and erasure coding.

Challenges of SDS:

Performance — SDS rarely matches the peak performance of specialised storage, especially for synchronous writes.
Setup complexity — especially for open‑source solutions like Ceph, which require experienced engineers.
Support — with open‑source software, you rely on the community or external integrators.
Network load — distributed systems generate significant network traffic for replication and rebalancing.

6. How to Choose Servers for SDS

Selecting the right servers is critical for SDS. Consider the following:

Storage subsystem — for Ceph and vSAN, use NVMe/SSD for journals and cache, and HDD for data. Ensure the server has enough drive bays.
Network interfaces — require fast networks (10/25/100 GbE) with RDMA support to minimise latency.
Memory — for caching and metadata. Ceph recommends 1–2 GB RAM per TB of data.
Processors — not necessarily the fastest, but sufficient to handle I/O and erasure coding calculations.

Our rack servers from Dell, Huawei, and Lenovo are ideal for SDS deployments. For example, Dell PowerEdge R660 with its NVMe‑optimised architecture is an excellent choice for high‑performance SDS clusters.

Planning an SDS deployment and need hardware selection advice? Contact our engineers

7. Frequently Asked Questions (FAQ)

Is SDS the same as hyperconverged infrastructure (HCI)?

Not exactly, but they are related. SDS is storage software. HCI is an approach that combines compute, storage, and networking in a single node. SDS is often a component of HCI solutions (e.g., vSAN is SDS within VMware’s HCI).

Can I use SDS for high‑performance databases?

Yes, but with caveats. For OLTP systems with strict latency requirements, traditional all‑flash storage is better. However, for analytical databases (OLAP) and Big Data, SDS can be an excellent choice.

Is SDS more difficult to manage than traditional storage?

It depends on the solution. vSAN is managed through vCenter and is relatively simple. Ceph requires more expertise but offers powerful monitoring and automation tools. In general, SDS requires more skills during initial setup, but management becomes easier over time with automation.

What network is needed for SDS?

At least 10 GbE is recommended; for heavy workloads, 25/100 GbE with RDMA (RoCE) is advisable. For clusters with many nodes, low latency and high bandwidth between nodes are essential.

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In the next article, we will cover the top 5 storage selection mistakes and how to avoid them. Stay tuned!