Most companies considering an enterprise SAN already have hybrid storage architectures. That is, they have some of their storage and processing resources centralized in a data center and other resources spread between various departments. Often both the data center and at least some of the departments already have local SANs. The challenge is to make the information on those local SANs available enterprise-wide while making best use of specialized resources such as backup facilities and do it at the lowest possible cost.
One popular solution is what is called a hybrid, mixed or core/edge architecture. In this architecture the central facility, or core, is fitted with a high-capacity, highly scalable device such as a director and the departments (edges) use less expensive devices such as switches to connect their SANs to the core SAN.
Hybrid solutions have several advantages when integrating SAN islands into an enterprise-wide architecture. They are relatively inexpensive, highly reliable, maintain the independence of the departmental SANs for most storage needs, allow the sharing of information across the enterprise, and maximize the use of resources such as centralized backup and data warehouse databases.
EMC discusses core/edge architectures, along with other options, in a white paper titled "Designing an Enterprise Storage Network to Manage Growth and Change", which is available at the company Web site at www.emc.com.
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.