Core-edge SAN switch architecture
How should you connect your SAN? There are a variety of ways, and this tip discusses one of the more complex of them. This is a follow on to our previous tips on cascaded and meshed SAN switch architectures.
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The third major architecture for a multiple switch SAN is core-edge. Bill Peldzus, the storage consulting marketing manager at Imation's (www.imation.com)Storage Professional Services Group, says that a core-edge architecture relies on layers of switches with at least two switches in the middle layer (for redundancy) and all the switches connecting to the switches in the next layer up or down. "This is incredibly scalable and gives good performance when you understand where to place your servers and your storage," Peldzus says.
However, a core-edge architecture is expensive because it uses so many switches. Further, the switches in the middle ('core') of the fabric are often directors, which are more capable and cost more than the switches at the outer layers (the 'edge' of the network.)
One important consideration, Peldzus says, is how the storage and servers are arranged. In general you do not want to put all the storage on one layer and all the servers on another because that increases the average number of switches data must travel through ('hops') to reach its destination, which will decrease overall data throughput.
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.
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Storage Area Networks: Designing and Implementing a Mass Storage System, 1/e
by Ralph Thornburgh and Barry Schoenborn
Online Price: $39.99
Publisher Name: Prentice Hall
Date published: September 2000
Whether you're considering a SAN for the first time, or you want a comprehensive management reference for the SAN you've already invested in, this book offers the insights, techniques, and guidance you need right now.
This was first published in September 2001