NAS and SAN converging but debates remain

Posted on March 01, 2003


Although confusion exists over just what NAS-SAN convergence is, it's clear that some users have a need to merge the best of both worlds.

By Alan R. Earls

NAS-SAN convergence may be inevitable, but what it actually means depends on a number of factors, including who you talk to.

Take the example of the Texas Children's Cancer Center (TCCC), where direct-attached storage systems were consistently running up against capacity limits. According to Dat Diep, senior systems engineer, when he arrived at the organization two years ago, key data was scattered among 13 Hewlett-Packard servers. It was difficult to search for data, and disk space was constantly running low on the servers. The only solution seemed to be a storage area network (SAN).

However, HP had an alternative recommendation for TCCC: Implement a StorageWorks NAS b3000 system, one of a new generation of network-attached storage (NAS) products that aims for SAN-like performance using NAS technology. While there's no actual SAN at TCCC, Diep regards this as a clear example of the convergence of NAS and SAN—at least from a performance, as opposed to architecture, standpoint.

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TCCC wasn't in a position to spend the money required for a large SAN solution. The HP NAS b3000 seemed to offer something comparable at lower cost so TCCC took the plunge. "It provides redundancy, availability, and the ability to increase disk space on-the-fly," says Diep, adding that the biggest single advantage was that storage became more manageable.

"Convergence" stories like Diep's are becoming more common, but they vary widely in details. Almost everyone agrees that by any measure—reliability, capacity, and speed—SAN and NAS are starting to look more and more alike. And, with some combinations of hardware and software, SAN and NAS are starting to act alike, too. A new generation of hardware and software is even permitting SAN and NAS to operate as a single entity. However, more often, SAN and NAS remain as mixable as oil and water.

Nevertheless, many users do have the need to merge NAS and SAN. In a QuickVote survey of InfoStor readers, of those that had both NAS and SAN, 64% said they had the need for products that merge, or combine, the two architectures.

A lot of the talk regarding NAS-SAN convergence revolves around recent announcements from Network Appliance. Last year, NetApp announced a unified storage platform, the FAS900 series (see "Network Appliance enters SAN market," InfoStor, November 2002, p. 1). The FAS900 is the company's first storage appliance to support both NAS and Fibre Channel SAN environments.

"When they came out with their SAN announcement, Network Appliance finally acknowledged that some things fit better in SAN environments and some in NAS environments," says Dianne McAdam, an analyst with The Data Mobility Group.

"It's no longer a NAS vs. SAN fight," says McAdam. "That 'religious war' seems to be over." Indeed, almost all vendors that used to take a black-and-white view, whether they offered SAN or NAS products, have softened their rhetoric. The result, says McAdam, is that NAS-SAN convergence is now part of a larger conversation in which it is also possible to have rational discussions about iSCSI and InfiniBand.

"People are finally realizing it's no longer a question of SAN or NAS, because they can co-exist," agrees Nancy Marrone, an analyst with the Enterprise Storage Group. Marrone says both architectures have a role, and they can be combined to address specific requirements. "Someday," she adds, "users may not know the difference."

Brad Nisbet, an analyst at International Data Corp. (IDC), says NAS-SAN convergence takes on a number of different guises. One of the most common is NAS heads (a NAS engine without internal storage) connected to SAN back-ends. "When I think of convergence, I think of NAS heads that sit in front of a SAN," says Nisbet. In this configuration, the NAS heads are often referred to as NAS gateways. This technology has gained traction at the high end of the market and is gradually migrating down toward the midrange market. While NAS heads are not yet widely deployed, they are available from several vendors, including Auspex, Dell, EMC, HP, IBM, NetApp, and Procom.

The next approach to convergence, according Nisbet, is "hybrid" devices that combine NAS and SAN in the same box. LeftHand Networks is an example of an early player in this market.

"An underlying question that is being answered in a variety of ways is, 'Where is the NAS functionality going to live?' " says Nisbet. Traditionally, NAS has meant a box with internal disks. Now vendors are separating the intelligence from the disks. That intelligence can now reside almost anywhere—in a traditional NAS filer, NAS head, blade device, switch, or as a function within a storage array.

Offering a similar view on convergence, The Evaluator Group's Randy Kerns notes that there are "several distinct solutions that are called convergence." In particular, though, Kerns focuses on what users are actually doing with the technologies.

"Typically, NAS buyers and SAN buyers are different people with different reasons for buying," says Kerns. Thus, the idea of a converged, one-size-fits-all storage architecture may not be the best solution.

Indeed, Kerns questions many of the marketing premises behind NAS-SAN convergence, particularly the notion that enterprises need to use SANs and NAS in overlapping ways. For example, he believes that at most organizations, storage devices used for block-level database transactions are not, in fact, the same resources required by file-oriented applications. "You really need to review the business case for convergence," he concludes.

A common thread

Eric Sheppard, an IDC analyst, makes a similar case against rushing to NAS-SAN convergence. Among the large number of companies that have deployed NAS and the smaller number of companies that have deployed SANs, there may be a common thread of wanting to achieve higher storage utilization and better ROI, he admits. However, Sheppard suggests that entry-level NAS users are, for the most part, perfectly happy with that architecture.

"At the high end of the market, it might make sense to pool storage resources and combine file-level and block-level access," he says, "but in the middle there is a fuzziness where convergence doesn't really seem necessary."

Bruce Hillsberg, director of storage software strategy at IBM, says his company is promoting convergence based on what customers are demanding. IBM's NAS Gateway 300 is a NAS filer that sits in front of a SAN and serves files from the SAN. "Some users want NAS in remote departments to enable file sharing, and some want to integrate NAS into their glass house environment," he says. Hillsberg says that IBM's Storage Tank initiative focuses on providing a consistent management approach across SAN and NAS resources.

Mark Nagaitis, director of product marketing at HP's infrastructure and NAS division, sees consensus emerging among vendors and users. He says that market confusion started about two years ago as SAN and NAS vendors made competing claims for their respective technologies. "The enterprise customer now understands that the ability to provide files to clients and blocks to applications is a universal requirement," he contends.

To Nagaitis, NAS-SAN convergence is the ability to provide NAS and SAN functionality using a single, managed pool of storage. HP has provided NAS devices that can connect to HP StorageWorks-based SANs since late 2001 when the NAS e7000 was introduced. Since then, HP's NAS strategy has been built around the concept of convergence. "In the majority of cases," says Nagaitis, "our NAS devices provide NAS services to users by connecting with SAN storage." In addition, HP also offers a number of stand-alone NAS servers.

A customer running a database on a NAS box is doing so, argues Nagaitis, not because it is the best technology but because it is simple and easy to manage. However, he says that the best way to do this is with NAS-SAN convergence. The database server should connect directly to the SAN, and NAS users should connect to the NAS device, which in turn, connects to the SAN. In this way, he says, each user gets the highest-performance connection to data while the associated management tools provide the simplicity in a combined NAS-SAN environment.

Necessity of compromise

Mark Amerlang, director of field and industry marketing at Auspex, says there are no real obstacles to convergence—except the necessity of compromise. "This is not an argument over blocks versus files, but a necessity to satisfy differing needs," he says. In his view, IT organizations see a need to consolidate storage and manage it as a central pool. But while some users such as engineering groups may not object to consolidation in principle, they find they can't give up file sharing. So they compromise. All the storage is consolidated and managed at a block level, but some of the data is allocated to a NAS engine that serves it out over the network at a file level. When that's done, "everyone wins," says Amerlang.

Auspex makes a vendor-independent Network Storage Controller for NAS/SAN operations. Amerlang argues that an open systems approach is critical to successful implementation of a convergence solution, because customers do not want to be locked into buying a NAS head from the same vendor from which they bought their SAN.

Still, IDC's Nisbet offers a few notes of caution: For internal political reasons, if not for valid technical reasons, unifying SAN and NAS islands may be impractical or unnecessary. "Convergence is not for everybody," he says.

"The most reasonable way of looking at it is based on customer requirements," says Jamie Gruener, an analyst at The Yankee Group. "It comes down to what applications you are using and whether there is any kind of flexibility in their need for either block or file access," he adds. "I think convergence makes sense because it should make storage easier to manage, but today only a few approaches are really able to do this."

Alan Earls is a freelance writer in Franklin, MA.

Procom upgrades NAS filers/gateways

By Dave Simpson

This month, Procom Technology added the NetFORCE 4000 series to its line of network-attached storage (NAS) filers, which can also function as NAS-SAN gateways via the company's DUET server option.

Most of the enhancements over the NetFORCE 3000 are in hardware upgrades. Although performance specs were not available at press time, the company expects a 2x performance increase over the NetFORCE 3000 series, due, in part, to a Xeon-class motherboard, 3GHz CPU, 533MHz front-side bus, 4GB of RAM, and dual active-active controllers (from LSI Logic). Maximum capacity is 16.35TB, or 32.7TB in a DUET clustered configuration. In a clustered setup, the filers can be equipped with a Brocade Fibre Channel switch.

In addition, Procom shrunk the NAS head into a 2U form factor and integrated one-inch drives in a JBOD configuration. The back-end connection supports 2Gbps Fibre Channel ports (two per NAS head) for NAS-SAN integration and support for both file-level and block-level I/O.

The 4000 series is expected to compete directly with systems from EMC (Celerra) and Network Appliance (FAS900). According to John Hamrick, director of marketing at Procom, the NetFORCE 4000 offers similar functionality as NetApp's FAS900, but at a lower price. A 292GB NetFORCE 4100 is priced at $75,000, while a 16TB version is priced at $300,000.

In a clustered configuration (Model 4200c), pricing ranges from $150,000 to $500,000 for a 292GB and 32TB version, respectively.

Originally published on .

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