"Unified storage" is a term most often used to describe a storage system that supports both block and file storage
protocols. Unified storage systems came about after years of battle between NAS and SAN vendors for storage dominance, when the market realized that it shouldn't be an either-or question and that customers needed both.
Unified storage systems promise savings in CapEx by reducing the number of physical storage components required, as well as the software that's purchased with storage hardware. A single, unified storage system has lower OpEx as well, since it's simpler to manage and cheaper to maintain. Less hardware also means lower costs for software maintenance and less overhead for IT admins. And, a single storage pool that can be used as file or block storage is more flexible since it allows IT to provision all available storage for any use case.
Today, the need for file storage has been well established and the benefits of file storage consolidation are something that IT organizations of all sizes are interested in. Consequently, most of the established storage vendors are coming out with a unified offering, and new products are appearing with the ability to provide both block and file storage capacity.
Unified storage architecture
Most unified storage solutions (which are also referred to as "multiprotocol storage," although that term has other connotations as well) use one of two basic controller architectures: modular or integrated. Modular unified systems have a separate NAS controller that handles file services for the storage capacity that's assigned to it. Integrated systems, on the other hand, implement that NAS functionality in software running on the primary storage controller, which provides both block storage allocation and file services.
Originally, all unified offerings were of the modular variety (except NetApp Inc.'s). SANs were the incumbent platform for shared storage, and adding a NAS head was the simplest way to add file services to an existing product. But with new system designs, multiprotocol support is being implemented in the storage controller, making the integrated architecture more common.
Examples of unified storage
We won't get into all of the unified storage solutions that are available, but a few are noteworthy. NetApp was essentially the first enterprise storage vendor to offer an integrated unified system with its FAS series of products, which provided Fibre Channel (FC), iSCSI, CIFS and NFS support for all sizes of deployments. Currently these products range in size from a handful of drives in a 2U chassis to a multiple-rack system that scales into the petabytes.
Nimbus Data Systems Inc. sells an all-flash storage system with a full complement of storage array features, including multiprotocol support. Nimbus' integrated controller handles block and file protocols (FC, iSCSI, NFS, CIFS and Infiniband) in either a scale-up or scale-out architecture. The company was the first on the market with an all-flash unified storage system, and it may still be the only one.
Starboard Storage Systems Inc. has a hybrid storage appliance that offers both file and block capabilities in an integrated architecture. Hybrid storage systems include flash and spinning disk capacity in the same chassis with a tiering and/or caching software layer that strives to keep the most active data on flash storage. Starboard's AC Series offers FC, iSCSI, NFS and CIFS protocol support. Although Starboard was the first to deliver a unified hybrid storage system, it has since been joined by others.
Hitachi Data Systems Corp. acquired BlueArc in 2011 and put its SiliconFS into the HUS 100 family of storage systems. These modular unified systems offer file and block storage, as well as object-based storage.
Modular vs. integrated
Which unified storage architecture to go with when looking at unified systems is probably a decision based on availability more than functionality. Modular solutions may be more appropriate for users that have an existing storage array that offers NAS services with a gateway module. On the other hand, users buying new unified systems will be looking mainly at integrated systems, since most of the new products will have an integrated architecture.
At one time block storage supported the most important applications, typically production databases, and file storage was associated with user home directories and office productivity applications. But now even the most critical databases are being run on NAS devices.
Server virtualization has further raised the profile of file storage, since applications like VMware store and manipulate entire server instances as individual files. NFS-hosted images are rapidly gaining traction in these environments. "Big data" archive systems in industries such as media and entertainment, oil and gas, and remote sensing, to name a few, also do their work at the file level.
Companies need file storage as much as -- or more than -- they need block storage, so multiprotocol support looks like a must-have for storage systems moving forward. Like snapshots, replication and data reduction technologies, being able to include "unified" on the spec sheet will become a selling point. File data is the source of most of the capacity growth in companies, and being able to accommodate that growth, in addition to providing block storage, with a single storage system is very appealing.
For the VAR's customer, it often seems there are too many vendors selling too many products that are all called the same thing, in this case "unified storage." As is the case with most newer technologies, VARs need to get comfortable with the details and be prepared to explain unified storage to prospects and customers. Like many other product choices that VARs make in specific accounts, the decision to go with a modular or integrated unified system may hinge on what storage assets are already in place and which unified offerings are available from the vendors they're engaged with in each account.
About the author:
Eric Slack is a senior analyst with Storage Switzerland.