Software-defined storage (SDS) is a radical new way to deploy storage services that promise to lower the cost of...
storage, improve performance and increase flexibility. Like most technology trends that have been deemed "hot," vendors have flocked to the term SDS to help describe their various approaches to the market.
SDS brings great flexibility to IT buyers and managers because it provides a single software interface to potentially all storage hardware, regardless of vendor. This means functions such as creating a volume, establishing RAID protection, implementing thin provisioning and data tiering can all be done through a single interface. IT administrators don't need to be re-trained on each storage system.
This flexibility allows organizations to purchase storage systems that are specific to a task without adding to infrastructure management. For example, a storage system that is suited for virtual desktop infrastructure can be used alongside a system that is better suited for high-transaction databases while being managed from a consistent interface.
Plenty of storage vendors make excellent storage hardware, but have not invested in the accompanying storage software. These vendors are often classified as Tier 2 vendors, but when coupled with SDS, they can match Tier 1 hardware vendors feature for feature. Examples of vendors in this space include Promise Technology and Imation Nexsan. At the same time, Tier 1 hardware vendors often have a hardware-focused product in their portfolios, such as NetApp's E series and Dell's PowerVault line.
Or, IT planners can use SDS to build their own storage systems. Companies like Super Micro and Seagate's Xyratex offer storage servers ideally suited for SDS products. These are typically rack-mounted modules with plenty of compute resources and expansion bays for hard drives or solid-state drives.
When considering this build-your-own-array category, hyper-converged SDS products are an option. These products are designed to run at or within the hypervisor and aggregate storage capacity across nodes within the hypervisor cluster. The result is a converged infrastructure of compute and storage.
An often overlooked benefit of SDS is that it puts the software purchase and hardware purchase on different buying planes. In the old, bundled model, when a data center needed to upgrade storage hardware, it was often forced to buy new storage software to go with the new system, even though the storage software was essentially the same as that running in the previous generation of hardware. In this model, hardware vendors were effectively charging IT again for something they already owned.
Software-defined storage vendors: How they break down
There is great debate among the many vendors of software-defined storage (and everyone else, it seems) as to what "true" software-defined storage is. I see the emergence of two distinct categories: software-only SDS and vendor-provided SDS. The first, a pure software product, is probably the original intent of SDS.
Software-only SDS: Vendors in this category provide the software without associated hardware and allow you to assemble your storage by aggregating existing storage resources or building your own storage array. These products should provide cost reduction and increased flexibility benefits.
Software-defined storage companies in this space are almost too numerous to mention, but they include DataCore SANsymphony, FalconStor Network Storage Server (NSS), Nexenta Systems and StarWind Software. These vendors are all primarily software-focused. The software-only SDS model enables users to install their software on a suitable piece of hardware and provide a set of common storage features to a variety of storage systems. Several of them can also run in a hyper-converged mode, allowing their storage software to be hosted in a virtualized environment.
Notably different is EMC ViPR, which is an SDS product that abstracts command and control over the storage hardware but uses the storage system's unique services. It provides a common interface to the snapshot command, but ViPR then tells the storage hardware how to use its own capabilities to perform the action.
Initially, EMC planned to provide a common command and control interface across its own storage platforms. Each of these had its own way of performing various storage services. Subsequently, EMC has added support for alternative vendors like NetApp and Hitachi Data Systems (HDS), as well as commodity hard disks. It has also added features that are not available in its core systems, such as an HDFS interface that brings a Hadoop connection to the platform as a whole.
IBM SAN Volume Controller software and the HDS Virtual Storage Platform are another set of outliers. They both run on dedicated, purpose-built hardware, but allow the attachment of virtually any vendor's storage hardware. The basic strategy for these two products is to use the virtualization component to aggregate the prior vendor's hardware into the HDS or IBM umbrella while encouraging all new purchases to come from them. Despite that strategy, nothing would prevent a customer from incorporating other new hardware from alternative vendors into the infrastructure.
Vendor-provided SDS: This category is software-defined storage that comes bundled with the storage hardware. These vendors have applied the basic tenets of SDS (abstraction of software from hardware), but still bundle the software with their specific hardware. This provides the vendor with flexibility, but not the customer. While this type of software-defined storage may not be considered "true" SDS, it can still have value for a customer. It does allow the vendor -- and subsequently the customer -- to transition to new hardware technologies more quickly. And if the vendor separates the software upgrade process from the hardware upgrade process, it eliminates the double charge described earlier.
SDS vendors in this space include Dell, IBM and many of the startups. These vendors have all focused on the software capabilities and have begun to incorporate more off-the-shelf storage hardware. Even EMC, to some extent, has done this with its VMAX systems.
While software-defined storage purists may have an issue with bundled SDS, I believe it can be legitimately included in this discussion. These products should allow the vendor to pass on cost savings to the customer and provide some flexibility in hardware migration. The level at which these benefits are realized largely depends on the vendor, so a customer should carefully investigate each software-defined storage vendor for its capabilities.
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