Software-defined storage is quickly catching on as a top technology trend in the storage industry, but the exact meaning of the term, and indeed whether it represents a new paradigm or just another marketing buzzword, is the subject of hot debate.
For smaller vendors looking to make their mark in the storage industry, the idea of defining storage services with software independent of the underlying hardware is appealing as it gives them an opportunity to even the playing field with their larger, more well-established competitors.
However, larger vendors, for whom the traditionally close tie between hardware and software lets them optimize storage services and performance, have to carefully tread into the concept of software-defined storage or risk cannibalizing their existing product lines.
There is no single industrywide definition of the term "software-defined storage." However, it can be thought of as a software layer that provides storage services, including such functions as deduplication, replication, snapshots and thin provisioning, using industry-standard server hardware.
Software-defined storage is not storage virtualization. Storage virtualization allows the capacity of multiple storage devices or arrays to be pooled so that it appears as if it is sitting on a single device. Software-defined storage is not about separating capacity from a storage device, but instead is about separating the storage features, or services, from the storage device.
The term is relatively new. Virtually unknown a year ago, it became one of the biggest IT industry buzzwords starting shortly after VMware's blockbuster $1.2 billion acquisition of Nicira, which was a large sum for a relatively unknown developer of another technology that was just starting to build momentum: software-defined networking.
That acquisition also gave VMware the base from which it could introduce the software-defined data center, or technology which allows all the functions of a data center to be defined by software instead of tied to hardware. And since VMware already had software-defined computing via its server virtualization technology, and software-defined networking via its Nicira acquisition, as well as a small organic project, the idea of software-defined storage seemed to be a natural fit.
For Keith Norbie, vice president of Nexus, the Minnetonka, Minn., office of Atlanta-based solution provider Stratos Management Systems, software-defined storage is a combination of trend and hype.
"The whole reason the term exists is to give storage the play the software-defined networking movement has," Norbie said. "The problem is, we already have software-defined storage. But we lack the ability to really define it."
The movement toward software-defined storage is already on with such technologies as VMware's vSphere VASA (vSphere APIs for Storage Awareness) or VMFS (Virtual Machine File System), or in such converged infrastructure offerings as the FlexPod reference architecture developed by NetApp and Cisco, or in the EMC-Cisco joint-venture VCE, or in companies like Nutanix, Norbie said.
What's missing is the kind of APIs that would make software-defined storage an integrated part of the software-defined data center, he said.
Norbie said to think of the software-defined data center as a Logitech Harmony remote which, when used with a home theater system, controls everything with the press of a button.
"In a way, that's how software-defined-everything should be," he said. "One button to do all the automation. Today, no vendor has that technology that works with everything ... We just lack all the controls for an extra management function. Storage is a component, networking is a component, compute is a component. We have control with compute and networking. Storage will be the hardest one."
Smaller storage vendors, especially startups, are quick to say that software-defined storage is a reality.
Jerome Lecat, CEO of Scality, a San Francisco-based developer of scale-out storage technology, defined software-defined storage as a platform built from x86-based servers where all the intelligence and storage-specific capabilities are provided by software.
"With software-defined storage, the storage is not in an array," Lecat said. "It's in servers and disks. We're not using any arrays."
Lecat admitted there is some hype in the term software-defined storage. "It's like when people talked about 'cloud-washing,' which was the tendency to apply the word 'cloud' to everything," he said.
However, Lecat said, the storage industry has been talking about software-defined storage for years even if the term was not yet used.
"We talked about this for three years," he said. "In 2011, I had to use long sentences to describe it. Now, I say SDS, and people get it."
Software-defined technology is here to stay, and will definitely be widely deployed, Lecat said. "Will this term stay in use?" he said. "I don't know. But the concept will be there."
Joe Arnold, CEO of San Francisco-based startup software-defined storage developer SwiftStack, also said the term makes it easier to describe what companies like his are doing.
"A year ago, we had trouble describing what we do," Arnold said. "We said we were decoupling our controller from the underlying hardware. Then we heard the term, and it clicked."
Software-defined storage is a way of looking at storage not from the disk or flash perspective, but rather in terms of what storage services are offered separate from the hardware, said Steve Houck, COO of DataCore Software, a Fort Lauderdale, Fla.-based developer of data management and protection software.
Storage used to be seen in terms of disk capacity, hardware and speeds, Houck said. "With software-defined storage, we look at it from the software layer and the value it presents on the hardware, he said. "It's very much about looking at storage from the device level or virtualization level."
Software-defined storage is causing a power shift in the storage industry from an innovation perspective away from larger, more established hardware-focused storage vendors, Houck said. "As companies get larger, organic innovation is a lot tougher," he said.
While startups and smaller software-focused vendors are quick to define software-defined storage as a way to replace legacy storage hardware with commodity servers, disk drives and flash storage, large storage vendors are not giving ground in terms of the value their hardware offers as storage functionality moves toward the software layer.
For storage giant EMC, the push is on to define its software-defined storage strategy while ensuring the company minimizes the potential impact on its existing storage technology business.
Amitabh Srivastava, president of advanced storage at EMC, said customers will be looking to cut management costs even as they look for increased storage automation, and will be looking for flexibility in vendor choice and how capacity is acquired.
"We have to pause and rethink how data is stored, and how it is managed," Srivastava said.
EMC's definition of software-defined storage includes capacity that is scalable across multiple geographies, and across commodity servers or on EMC or third-party arrays; the ability to virtualize all the underlying storage into pools; and open APIs so any vendor, partner or customer can build the controllers needed to access the underlying storage hardware, Srivastava said.Because of EMC's storage software capabilities and its commodity x86 server-based hardware, the company has an advantage over software-defined storage startups that can provide only parts of the entire infrastructure, Srivastava said.
By making its APIs openly available, EMC can be at the center of the software-defined storage movement, he said. "Building a product is not enough," he said. "You need to build a community ... We're opening up APIs so new services can be built by partners or customers."
Srivastava also said it is important to remember that different storage hardware offers different capabilities, making it possible to differentiate one vendor's hardware from another's even as software-defined storage is adopted.
For example, EMC's Isilon line is designed for scale-out storage applications, while EMC's VMAX line is designed for performance and high availability. "I don't know how the mix will change or not," he said. "We're going to provide value with the unique systems we are building."
Srivastava said EMC is planning a second-half 2013 release of its first software-defined storage technology, which takes advantage of all the capabilities he outlined.