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				Common SAN designs
				There are many possible design possibilities when creating a storage area network (SAN). Josh Judd, author of Multiprotocol Routing for SANs, identifies the most common SAN design options.

Storage area networks (SANs) remain complicated beasts. Despite vendors' efforts to simplify SAN implementation and management, they remain difficult to build, maintain and manage. Surprisingly, there are only a couple of SAN design tools that help storage administrators to design and update a SAN over time.

The need for SAN design automation is clear. "As soon as you go beyond a SAN that is small--maybe one switch and a few devices--you can't design it with paper and pencil, a spreadsheet or a whiteboard," says Bill North, director of research, storage software at International Data Corp. (IDC). "Everything just breaks down."

For most organizations, expanding a SAN is a trial-and-error process. SAN design projects rarely start with a blank slate; instead they expand or consolidate storage that's in place. Storage managers need to decide what works with what and how best to connect all the SAN parts together.

Outside consulting firms are frequently brought in to design a company's SAN. They navigate the minefield of interoperability considerations and constraints, document the resulting SAN environment and train staff to maintain it.

Regardless of how well planned and designed the SAN may be, it will invariably change. Keeping track of what you have, matching compatibility among components at every layer of the protocol stack, and ensuring everything is connected correctly and that redundant links are where they need to be becomes a labor-intensive task. Lack of up-to-date SAN documentation makes the job even more difficult.

"You need a way to design [the SAN], automatically discover what is there and [then be able to] compare it to what you planned," says North. This requires an automated SAN design tool.

To date, only two vendors offer SAN design tools: Computer Associates (CA) International Inc. has its BrightStor SAN Designer, while EMC Corp. provides SAN Architect. In addition, Boston-based Onaro Inc. offers SANscreen, a SAN change management tool (see SAN design tools). "That's about all [the companies] that do SAN design," says Randy Kerns, senior partner at the Evaluator Group Inc., Greenwood Village, CO. However, there are numerous vendors with storage resource management (SRM) and SAN management tools that offer various levels of automated device and topology discovery.

"You'd think there would be more SAN design tools, but there aren't," says Kerns. CA and EMC acquired their SAN tools from two small vendors, Netreon Inc. and Prisa Networks, respectively. "Tools like these should probably be integrated into bigger SRM and SAN management solutions," he adds. CA has made BrightStor SAN Designer a component of its larger BrightStor SAN management suite, while EMC offers SAN Architect as part of its ControlCenter family.

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