Unified Storage: What Is It Good For?

There was a time when single-tasking data center equipment was all the rage. CPU cycles and RAM were at a premium, so it made sense to design equipment that did one thing and did it well. Intel has exploded this old assumption thanks to the continual proliferation of transistors according to Moore's Law: Today's processors, network adapters and buses have CPU cycles to spare, and most data center equipment is turning to software for differentiation.

Enterprise storage providers have long produced single-tasking devices. NetApp was the king of network attached storage (NAS), EMC ruled the enterprise storage area network (SAN), and most smaller applications made do with direct-attached RAID shelves. But then a funny thing happened: iSCSI. Suddenly, NetApp had a convincing SAN alternative that used commodity Ethernet and PC processor hardware.

Although price reductions due to the commoditization of enterprise storage have received a great deal of press, NetApp found itself in possession of another unique differentiator: Its SAN and NAS storage systems shared the same hardware and code base, and could be managed from the same interface. Thus was born the concept of unified storage.

Customers appreciated the idea that they could reallocate resources between the SAN and NAS components, and that the same management interface could be used for both. Although few actually repurposed storage in this way, unified storage became the rallying call of the NetApp marketing machine. With Fibre Channel, NAS and iSCSI all sharing the same code base and hardware, NetApp would became a one-product company.

The unified storage marketing message works so well, in fact, that many of NetApp's competitors came out with so-called unified products, as well. Some were truly monolithic products offering both SAN and NAS, while others were bundles of existing SAN hardware with a NAS front end. Some offered a single interface for configuration, monitoring and management, while others used separate point products for each of these tasks. Predictably, this set off a storm of protest from NetApp marketing regarding the definition of the term  "unified storage."But the buyers of these systems don't really care about the definition of term. What they cared (and care) about is their experience selecting, purchasing, operating and supporting a storage solution. Cobbling together a combination SAN and NAS storage system from two different products--each with its own management interface, idiosyncrasies and hardware--is not the kind of unification end users want. They care about the things that they see and interact with, much more than they care about packaging a product for sale.

The centerpiece of EMC's recent product launch is the new midrange VNX and VNXe array family. These are an evolution of the old Celerra/Clariion on NAS/ SAN product line, and EMC is pitching them as a unified solution. But through some under-the-hood magic, the VNX runs both Celerra DART and Clariion FLAIR storage stacks within a single storage controller. Since users will purchase a single piece of hardware and interact with it through the user-friendly Unisphere management interface, most will find this an acceptable alternative to NetApp's offerings.

Arguing over the definition of a term like unified storage is worthwhile as long as substantial differences in the experience of end users exist. Once system like the new EMC VNX become sufficiently integrated, however, such discussions become academic. NetApp enjoyed a decade of dominance in the unified storage space, but EMC has finally produced a credibly unified product.