Direct connect storage in the client/server storage model proved to have limitations in bandwidth, the maximum number of devices available on a bus, and concurrency of traffic. Attaching application servers and Fibre Channel storage devices to a central location creates a network of server and storage devices. This configuration allows the application servers to access the storage devices in a network fashion. In other words, the devices, both servers and storage, must have an address on the network, have the capability to log in, and have methods available to communicate with other devices within the network.
As depicted in Figure 4-6, servers and storage devices participate in the network. All devices log in to the network, or fabric OS, which is done by sending messages through Fibre Channel protocol frames .