Compare software-defined storage vs. storage virtualization

Software-defined storage

Most modern storage management approaches are software-based. SDS manages different types of storage devices independently of the storage hardware. SDS supports most administrative activities from a single user interface.

It simplifies updating storage software and uses commodity devices in storage arrays. SDS manages storage arrays in pools or other configurations based on user needs. It facilitates scaling out of devices to provide more capacity. SDS can also perform tasks such as replication and snapshots.

The rapid growth of unstructured data, scale-out storage expansion, virtualization of hardware devices and the growth of cloud-based storage have all supported SDS adoption. SDS applications are available from numerous vendors. There are also open source products including Ceph, FreeNAS and OpenStack Swift.

Advantages and disadvantages of SDS

SDS provides flexibility for managing storage resources, ease of administration, dynamic scalability and enhanced feature automation. Organizations can manage just about any arrangement of storage devices using an SDS application. They can use older legacy storage devices to save on costs instead of buying new equipment. Centralized storage management through SDS can also use technologies such as data deduplication, encryption and compression.

SDS software does not have to be from the same vendor as the storage systems. However, some commodity hardware may not be compatible with certain SDS configurations, so test the choice of SDS with hardware to determine the compatibility. SDS can also be difficult to manage in large environments, and organizations may need more personnel to handle the different types of hardware.

Storage virtualization

Storage virtualization centrally manages and aggregates multiple storage devices so that they appear to be in a pool of storage capacity. The storage pool can use standard configuration and architecture servers or VMs.

Virtualized block- and file-based storage are two common implementations of virtualized storage. The former option is unique to NAS systems. By contrast, file-based storage uses various protocols, such as SMB, CIFS and NFS. The file-based approach in storage virtualization removes the need for a NAS array that links data and physical memory elements.

Mapping of storage resources is a key part of storage virtualization. Organizations can use the maps to locate stored data. To respond to read and write requests, the virtualization software refers to its map to locate the requested data or to store data on a specific device. 

Advantages and disadvantages of storage virtualization

Storage virtualization was considered somewhat challenging to implement and manage because it originally ran on a host system and other devices used the storage pool. That has changed as updated and enhanced systems -- which are much more flexible and adaptable to user requirements -- become available.

Like SDS, important benefits of storage virtualization include ease of administration, scalability, efficient storage utilization, reusing older legacy systems and deploying features such as caching and replication across the storage pool.

The main limitation of storage virtualization is the chance of vendor lock-in, although product improvements have minimized lock-in issues.

Comparing SDS and storage virtualization

Both approaches to storage management abstract storage management activities from hardware platforms. Each provides increased flexibility of feature use and more independence from specific storage vendors, devices and infrastructures. Both options are important for business continuity (high availability), disaster recovery (replication to an alternate site), ease of expanding storage capacity and cost-effectiveness.

The use of commodity storage devices is often associated with SDS products as a key benefit. Customers must carefully examine the storage devices they currently use, or are planning to use, and identify the most cost-effective storage devices for their needs.

Storage vendors also offer SDS or storage virtualization software along with their hardware. Some vendors might charge more for the software because it has been optimized to work with their storage hardware. 

Planning considerations

As with any storage technology decision, practice due diligence. The following is a list of activities to perform when considering SDS and storage virtualization.

• Determine the business requirement for data storage, access, security and protection.
• Consider using the systems development lifecycle as the framework for planning and implementation.
• Examine existing storage technologies, policies, procedures, protocols and experiences to determine which option fits into the existing and longer-term storage infrastructure.
• Examine both types of product and services and evaluate standalone apps that can run in existing storage platforms as well as offerings from hardware and cloud storage vendors.
• Perform a cost-benefit analysis to determine which technology can reduce overall storage costs while expanding storage flexibility, capacity and ease of administration.
• Prepare a project plan to implement the selected approach.
• Consider using a multi-phase approach, starting with a small set of storage devices and expanding to larger storage arrays.
• Update storage policies, procedures, protocols and administrative activities to accommodate the selected approach.
• Provide training to IT staff and other employees as needed.
• Perform periodic reviews of the storage program and keep management informed of the technology and its performance and value.