Meshed SAN switch architectures
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How should you connect your SAN? There are a variety of ways, and this tip discusses one with medium complexity that may be suitable for your smaller installations. This is a follow-on to last week's tip on cascaded SAN switch architectures.
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In a previous tip, I discussed cascaded architecture for SANs. One step up in complexity is a meshed architecture. Bill Peldzus, storage consulting marketing manager at Imation's Storage Professional Services Group. (www.imation.com), says a meshed fabric provides an any-to-any connection, but it uses a lot of ports. "Say you have four switches connected every switch to every switch," Peldzus says. "Three of the ports on each switch would be dedicated to interswitch connection."
A meshed architecture is simple, multiply redundant and provides excellent performance because it minimizes hops through switches to pass data through the network. Its biggest drawback, Peldzus says, is that it doesn't scale.
"If you double the SAN to 8 switches, now you're burning 7 ports for interswitch connectivity," Peldzus says. "Pretty soon you hit the theoretical maximum based on how many ports you have on the switches." This is especially true since many SAN switches only have 8 or 16 ports.
A meshed architecture is only recommended for a single-fabric SAN that isn't going to grow. "If you are going to have more than two switches and it doesn't have to scale it works fine," Peldzus says. This meshed architecture is most suited to a relatively small SAN installation such as one supporting a work group or branch office.
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
Storage Area Networks covers it all: key concepts, components, applications, implementation examples, management, and much more. 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.