Chapter 3. What Makes a SAN Go

In this chapter, you discover how the devices in a storage area network (SAN) communicate with each other. Building a SAN is similar to building any other kind of data or voice network; it has three phases:

  • Making the physical connection between all network devices with cables

  • Initiating the directory in the network so the devices can find each other

  • Enforcing the set of rules (that is, the protocol) so each device knows how to communicate on the network

Understanding how all these pieces fit together in a storage network is useful when something goes bump in the night. If you have to troubleshoot a problem in a SAN, knowing how it's supposed to work will help you figure out why it's broken.

Networking Basics

In computing, a network consists of two or more elements (devices) connected over a common medium (usually a cable) and a process (or protocol) for transmitting data from a sender to one or more receivers. Pretty simple.

When you were a kid, did you ever try to create your own little phone network by using a string to connect two paper cups? Although it was probably a bit hard to hear your friend on the other end, the "phone" actually worked. The vibrations from your voice were transmitted over the string (the medium) to the paper cups (the devices), which allowed your friend to hear your voice, and you took turns talking and listening (the protocol); taken together, the cups and string were really a simple network.

Okay, that was fine for only two people, ...

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