Developing an effective design for a SAN is usually an iterative process. Unless the SAN is very simple, your requirements...
are very loose, or you're very lucky, the design you start with is not going to be the one that ends running the enterprise. With that in mind, Brocade offers several suggestions for working out a SAN design.
First and foremost, keep it simple. In general, the simpler the design (within limits), the more likely it is to work satisfactorily. The limits to that concept involve things like building in redundancy for reliability. However modern SANS are both flexible and scalable, which means it's easy to go back and make modifications and add links and switches later if needed.
Second, Brocade suggests a core-edge design for any but the simplest SANs. A core-edge architecture uses two or more interconnected switches in the center of the fabric with devices connected to other switches at the edges. The advantage of this approach, Brocade says, is that is combines extreme flexibility with scalability and resilience.
Brocade's third suggestion is don't re-invent the wheel. While a SAN should be as good a fit as possible to the needs of the enterprise, most vendors have a number of reference designs available for SANs aimed at meeting particular needs. Most of the time it makes a lot more sense to modify one of these designs that to start from scratch.
Brocade's suggested strategy for planning and designing a SAN can be found here.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.