The world's two main networked storage architectures -- SAN and NAS -- are breeding.
EMC, IBM and less well-known storage specialists such as BlueArc are beginning to mix and match the best elements of network-attached storage (NAS) devices and storage area networks (SAN) to improve the efficiency and lower the cost of storing data.
NAS boxes, which hook into existing Ethernet networks, are simpler to manage than SANs, but provide less performance and can top out on capacity. SANs generally are far faster and hold more data, but they can be expensive and result in cumbersome file sharing.
The Law Enforcement Support Agency of Tacoma, Washington, for instance, which provides services such as records management to local law enforcement groups, opted for a 6-terabyte "SiliconServer" system from BlueArc that is on the surface a NAS product -- serving files over an Ethernet network -- but promises the speediness of a SAN.
"We have not suffered any performance degradation," said David Reinker, an information systems manager at the agency. "In some cases, we've found it to be slightly faster."
BlueArc SiliconServer products allow for a SAN-like capacity of up to 256 terabytes in a single cabinet.
On Monday, the company unveiled a new product called "Titan SiliconServer," which also combines elements of NAS devices and SAN. The product can expand to greater capacities and adds features including the ability to increase system speed over time.
One sign of the push to merge NAS and SAN is the growing popularity of so-called NAS gateways. These are devices without disks of their own that can connect SANs with Ethernet networks. Worldwide revenue for NAS gateway products jumped 27 percent last year to $84m (Ã,£46m), according to market research firm Gartner. Gartner expects annual NAS gateway revenue to grow 27 percent between 2002 and 2007, reaching $215m in 2007.
By contrast, revenue of NAS equipment with integrated disk storage is slated to rise 16 percent during the same period, to $2.8bn in 2007, according to Gartner. SAN gear revenue is expected to increase 11 percent annually in the period, to $10.3bn in 2007.
The growing SAN-NAS convergence is part of a longer march toward more efficient use of disk-based storage resources and is similar to the trend of "virtualising" server computers. A decade ago, much of the data used by servers was held on storage systems directly attached to those servers. But those isolated "islands" of storage translated into low usage rates -- 15 percent to 30 percent of storage resources, said Brian Babineau, an analyst at market research firm Enterprise Storage Group.
In recent years, networked storage has emerged to create larger pools of capacity that administers can carve up for improved efficiency. Use of SANs and NAS hit about 50 percent in the late 1990s and the early part of this decade, Babineau said. Since then, companies have turned to management software to increase the efficiency, and NAS gateways can help get rates up to about 70 percent, he said.
Ups and downs of SAN and NAS
A typical SAN set-up could include a number of disk arrays that are connected to a switch that, in turn, is connected to a number of server computers. SAN disk arrays are sold by companies such as Hewlett-Packard, IBM, EMC and Hitachi Data Systems, while SAN switches are produced by Cisco Systems, McData and Brocade Communications Systems.
SANs traditionally have been used with programs such as database applications that access data at the "block" level. In contrast, NAS gear provides data access at the file level, which is a higher-level way of organising information. Block-level access is faster in a transactional database environment, because it requires fewer steps to locate bits, said Gartner analyst Roger Cox. Another key to SANs' speed is the use of the Fibre Channel interface, a technology that allows for data transfers at a rate of 2 gigabits per second (gbps). A standard has been approved that ups the data rate to 10gbps.
What's more, SAN capacity can be increased relatively easily by adding another disk array to the network. Drawbacks to SANs, though, include expensive equipment and difficulty in sharing files among users. Typically, sharing files in a SAN environment requires copying the data, which eats up storage capacity.
NAS boxes are dedicated computers that serve up files on a network. The devices are sold by companies including EMC, Network Appliance and Hewlett-Packard. Companies have used NAS gear to store files created in applications such as computer-aided design software or spreadsheet programs.
The file-level approach allows multiple users to share files without copying the data -- for instance, several automobile engineers could work on the same new car design at the same time. NAS devices also are relatively simple to install, without the need for switches or network adapter devices. But NAS systems are generally slower than SANs. That's partly because NAS devices typically rely on Ethernet networks, which transfer data at a rate of 1gbps. What's more, NAS systems as a rule are not as expandable as SANs.
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