SAN And NAS Join Forces

Companies like Network Appliance were touting NAS, which handles storage on a file-system level, as the disruptive technology to the more costly and complicated SAN technology. That argument, of course, did not sit well with big systems makers like EMC, which argued that NAS appliances could not possibly be the answer for mission-critical data because of an inherent scalability problem. But this marketing battle quickly morphed into what became known as NAS and SAN convergence -- blurring the definitions of these architectures so much that, about four years ago, it prompted a technology editor from a storage magazine to ask during a vendor product briefing: "So when did NAS suddenly become SAN?"

Fast-forward to today: Now SAN and NAS are regarded as complementary technologies. Consider the white paper sponsored by Brocade Communications Systems, titled "Comparing Storage Area Networks and Network Attached Storage." The author acknowledges that NAS and SAN often are seen as competing technologies. But in truth, the two technologies serve different storage needs. While both satisfy the need for customers to remove, or lessen, the number of direct-attached storage within their environments, SANs are centralized systems with their own dedicated Fibre Channel networks, optimized for the transfer of large blocks of data and used for mission-critical database applications. NAS devices, on the other hand, are file-serving appliances accessed by workstations and servers through a network protocol such as TCP/IP.

Everyone is willing to accept that NAS and SAN have their own purposes. Even EMC long ago introduced a NAS appliance called Celerra. And last month, Hitachi Data Systems (HDS) announced NAS products that are the result of a VAR pact with Network Appliance. HDS initially revealed the deal last December, in which Network Appliance was going to build a NAS gateway device that would work as the central nervous system to an HDS NAS solution. The children of that union are HDS' Freedom Storage and HDS-NetApp Enterprise NAS Gateway models, which comprise the GF940, GF940c, GF960 and GF960c.

Executives say HDS will be the sole VAR of the rack-mounted gateways, which include Network Appliance's Data On Tap operating system as well as the company's WAFL file system. Certain gateway models, such as the GF960c, work with HDS' high-end Lightning subsystem, while other models work with the HDS midrange Thunder disk subsystems. The Lightning and Thunder devices view the HDS gateway as just another server. So why bother to create a NAS gateway seen as just another server by the SAN-based disk arrays? The key reason is to solve the scalability limitation of NAS appliances, says Kevin Sampson, director of marketing for NAS at HDS. Moreover, it helps streamline the backup and recovery process between NAS and SAN. Any third-party backup software works the same on the HDS gateway as for SANs.

With this solution, HDS execs say, SAN and NAS can coexist. Sampson says HDS is starting to see customers doing more than file-sharing on NAS. They're starting to run mission-critical data,such as Oracle database applications -- on NAS. "What has happened over time is the line between SANs and NAS has been disappearing," Sampson says. "Customers want mission-critical data like medical records [quickly] … You have NAS that is starting to act more like SAN. Customers are expecting SAN performance from NAS applications."

It may be several years late, but that storage-magazine editor may finally have the answer to his question. n