By Sandra Gittlen
Network World, 9/28/98

Ask Dwight Gibbs, chief technical fool at online financial advisor The Motley Fool, if he thinks storage-area networks (SAN) are a bunch of hooey. He'll tell you he just bet more than $15,000 on them.

Gibbs is reconfiguring his corporate network to off-load storage from individual servers and move it to a SAN. SANs provide higher availability of data, broader scalability, easier management and improved server performance, according to vendors touting the newfangled networks.

While the definition of this new technology is a bit hard to pin down, most vendors and users think of a SAN as a group of storage devices hooked together via a high-speed connection that is accessible by multiple servers. The servers can run on heterogeneous platforms, according to International Data Corp. (IDC), a research firm in Framingham, Mass.

"The initial vision of SANs includes switches that provide dynamic any-server to any-storage connections and buildingwide, neighborhoodwide and campuswide topologies," a recent IDC report says. Storage devices can be linked via Fibre Channel, FDDI or any other non-network protocol.

Gibbs, who expects to have a SAN from Network Appliance installed by the fourth quarter, says his Web servers were getting bogged down because each needed to store the same information. He is going to move graphics files and static HTML files that don't have to be parsed onto the SAN. "Why spend $45,000 on a server just to have it bogged down with I/O duties?" Gibbs says.

Mainframe old-timers

About a year ago, Michael Peterson, president of Strategic Research in Santa Barbara, Calif., developed an alternative to network-attached storage. He thought network-attached storage was limiting because it relied on network protocols and didn't guarantee delivery.

Peterson suggested that SANs could be interconnected using network protocols such as Ethernet, and the storage devices themselves could be linked via non-network protocols. According to Peterson, SANs have three major components: the interfaces, including SCSI, IBM Serial Storage Architecture or Fibre Channel; the interconnects, such as extenders, multiplexers, hubs, switches and routers; and the switching fabric.

In a traditional storage environment, a server controls the storage devices and administers requests and backup. With a SAN, instead of being involved in the storage process, the server simply monitors it.

By optimizing the box at the head of the SAN to do only file transfers, users are able to get much higher transfer rates, such as 100M bit/sec via Fibre Channel. Traditional SCSI connections offer transfer rates of only 40M bit/sec.

Using Fibre Channel as the hookup between storage devices also increases distance options. While SCSI only allows a 25-meter stretch between machines, Fibre Channel supports spans of 10 kilometers. SCSI can only connect up to 15 devices, whereas Fibre Channel can link as many as 126.

"SCSI can be enhanced over Fibre Channel, but there are still addressing issues and performance issues with the protocol itself," CNT's Kelhoff says. "While Fibre Channel allows for 100M bit/sec transfer rates, the [SCSI] protocol implementations don't take full advantage of this."

SANs aren't cheap

"Building a SAN is not trivial - it's an expensive decision," Gibbs adds. He paid $10,000 for a hub and $5,000 for controllers for his SAN.

"This isn't something you can put together at Computer City," says Rob Davis, director of product marketing at Ancor Communications, a storage product developer in Minnetonka, Minn. Hewlett-Packard and Sun are building SAN capabilities into their storage boxes, Davis says.

But Thomas Nolle, president of CIMI, a consultancy in Voorhees, N.J., says, "SANs don't merit the attention they are getting." He doesn't believe the need for storage is growing at a fast enough clip to warrant all the notice.

Because SANs are highly centralized, they're better suited for data centers than networks, Nolle says. He says there are only two instances in which SANs would make sense: if you want all your mass storage in one place but can't make the physical connection with SCSI or if you need failover capabilities.

The next wave

Industry experts predict the next generation of SANs will take on additional duties in the network. "The next phase will be when servers aren't even dealing with requests," Ancor's Davis says. "Instead, the SAN will talk directly to the client."

Rick Franz, director of corporate marketing at SAN interface provider QLogic in Costa Mesa, Calif., says SANs will lead the way for other tasks to be off-loaded from the server. "Next, we'll take the file system off the server and put it into its own network," he says. "When you use the server to look at the file system on the network, then you allow it to act as a resource."