By contrast, revenue of NAS equipment with integrated disk storage is slated to rise 16 percent annually from 2002 to 2007, reaching $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.
