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.
Bridging the data storage divide
NAS gateways, also known as NAS heads, are one way to combine the best of both NAS and SAN. These products offer greater ability to add capacity compared with a traditional, self-contained NAS storage system, said Jim Holley, EMC's director of NAS platforms. "If you start out with an appliance, eventually you're going to outgrow that appliance," he said.
Using NAS heads also allows companies to tap into unused capacity on SANs. And the products permit customers to trim the number of administrators needed to manage storage, said John McArthur, an analyst at market research firm IDC. McArthur said companies now have the option of replacing multiple NAS devices with a NAS head that links to a large-capacity SAN system. "If you want to simplify your environment, you want to consolidate," he said. "It increases 'vendor lock-in,' but it brings down operational costs."
In mentioning vendor lock-in, McArthur highlighted the limited compatibility of NAS gateway products. For example, Network Appliance said its NAS gateway products work with SAN equipment from Hitachi Data Systems and IBM, but not EMC's. IBM's NAS Gateway 300 works only with IBM's FastT storage servers and Enterprise Storage Server products. EMC's NAS gateway products are compatible only with EMC storage systems.
Aside from NAS gateways, another approach to bridging NAS and SAN technologies is to allow for both "block"- and "file"-level data access in the same device. This is a route Network Appliance has taken with its so-called unified storage products. Since 2002, the company has offered disk-based storage devices that allow for both block- and file-level data access.
More and more customers are using the products to handle data in both ways, said Chris Bennett, director of product marketing at NetApp. "It's common, and it's becoming even more common," he said.
