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Software-defined storage in a nutshell: Why you need it now

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Linda Dailey Paulson, Freelance writer, infrastructure, Linda Dailey Paulson Associates

There is as much confusion as there is buzz about software-defined storage (SDS), which is rapidly becoming a key technology in enterprise data centers. A big reason for the confusion lies in the way in which software-defined storage—as with other software-defined infrastructure buzzwords—has been defined.

Some people refer to it as a wholly new form of storage, while others say it is an approach in which the hardware doesn’t matter because the software—and how it manages the hardware—is key. 

There may be no agreed-upon, industry-wide standard definition for this storage virtualization technology, but it's possible to narrow it down to the essentials you need to know as you consider it as a part of your software-defined data center strategy. Here, then, is software-defined storage in a nutshell.

What SDS is ... and isn't

The best place to start is with the Storage Networking Industry Association (SNIA), which describes SDS as “Virtualized storage with a service management interface.” According to the SNIA, “SDS includes pools of storage with data service characteristics that may be applied to meet the requirements specified through the service management interface.” It is, the organization says, more than just storage virtualization.

To be software-defined storage, a software-defined storage system must offer six things:

  • Automation
  • Standard APIs for the storage device management
  • Provisioning and maintenance
  • A virtualized data path
  • Scalability
  • Transparency (defined by the SNIA as “The ability for storage consumers to monitor and manage their own storage consumption against available resources and costs”)

Software-defined storage is a delivery model for storage rather than simply a new type of storage, says Scott Sinclair, a senior analyst with the Enterprise Strategy Group. Roughly 68 percent of all organizations are committed to software-defined storage as a long-term strategy, according to a recent ESG survey of storage administrators. Another 26 percent have interest in software-defined storage but no formal implementation plan.

So overall, 94 percent of organizations have a plan to adopt software-defined storage.

What's in it for you: Key benefits of SDS

The appeal of software-defined storage lies is in its ability to leverage existing storage and hardware assets. “You can use more media types than you would be able to do otherwise,” says Sinclair. Users are free to choose any type of hardware they wish. The secret sauce is in the software and how it provisions and manages the hardware through the use of policies, allowing users to become more agile in how they take advantage of virtualization without requiring the purchase of new hardware. It frees IT professionals to manage data, not the storage hardware.

The premise of software-defined storage, says Sinclair, is “taking the software that used to run inside a SAN array and offering it as software.” Instead of purchasing a SAN, IT need only purchase software that can run on any x86 server. Administrators can mix and match hardware and media alike. Storage becomes a heterogeneous pool of hardware resources. Users can also pull in cloud resources as needed or place storage on premises. The “where” no longer matters, so long as the data is stored somewhere. There’s no more need for IT professionals to “rip and replace.”

The two primary benefits of this approach are cost and efficiency. You can use all of your existing hardware and leverage it optimally before considering the purchase of new storage hardware. If an application is best suited to deployment in the cloud and the back-of-the-envelope numbers look good for such a move, you can deploy software-defined storage to support that.

You can stand up such systems quickly says Sinclair. Testing and evaluation are quick and easy, and there’s no need to get new hardware, providing more agility in deployment.

Key offerings in this space, according to Forrester Research, include HPE’s Storage-Refined Storage, NetApp’s ONTAP, and VMware’s Virtual SAN.  “All deliver an abstraction of physical layers, often described as a fabric, that allows the virtualization of the storage layer,” says Robert E. Stroud, a principal analyst at Forrester Research. The storage layer interacts with the hardware, allowing API layer integration with any applications that require storage resources. And EMC also offers several different types of software-defined storage technologies, adds Sinclair.

There are at least 40 different vendors, says Sinclair, depending on the definition of software-defined storage. “It is easier to list those who aren’t in the storage-defined space.”

Caveats: What's holding SDS back

Despite the the fact that all the necessary technology components are available for creating a “moderately complex" x86 software-defined data center, many IT organizations are still confused about features, scalability, and interfaces, and this has inhibited adoption, says Stroud.

Despite what seems like a compelling business case for moving toward this approach, users face three significant challenges associated with wider adoption of software-defined storage:

  • No single integrated solution exists that incorporates compute, storage, and network, although Stroud says that “there are good solutions within multiple domains, especially commute and storage.” This means many SDS systems require that enterprises purchase new hardware.

  • SDS won't work unless organizations change the operating model and culture first. “Developers need to realize that they no longer own servers,” Stroud says. “They need to simply write code that uses the resource pool.”

  • Standardization is critical to success. Instead of building "snowflake environments," enterprises need to choose standardized environments that they can manage and upgrade using the appropriate change management process.

Many IT organizations are also confused about how to best implement SDS. True commodity hardware doesn’t yet exist, says Stroud, and no matter how much users would like that to be the case, integration challenges remain. The hardware available may be similar, but each system may work slightly differently due to differences in firmware or other integration challenges.

One of the most compelling arguments for adopting the SDS approach is that it is hardware-agnostic, but IT organizations tend to gravitate toward tailor-made systems that combine the hardware of the customer’s choosing with SDS software, according to Sinclair. Although some buyers want the freedom to pick and choose, most customers prefer an integrated solution more than a choose-your-own hardware-software adventure, Stroud says.

SDS deployment: It's time to get moving

If it hasn't done so already, your organization should start moving to software-defined storage to reflect its commitment to flexible, agile infrastructure, say analysts. From an architecture standpoint, says Sinclair, “we’ll see more storage architectures moving to software-defined storage because of the flexibility it gives.” Most IT organizations will probably be most interested in integrated systems. "That's likely to be the deployment model for some time.”