Chapter 3: SAN Setup

Fibre Channel storage area networks (SANs) can be designed as both shared-media and switched-access networks. In shared-media SANs, all devices share the same gigabit loop. The problem with this is that as more devices are added, throughput goes down. While this may be acceptable for very small environments, a backbone based on Fibre Channel switches will increase a SAN s aggregate throughput. One or more switches can be used to create the Fibre Channel switching fabric. Accessing the services available from the switching fabric is possible only if the network interface card (NIC) of each storage device can connect to the fabric as well as to the operating system and the applications. Basically, the NIC becomes a citizen of the network by logging into the fabric. This function is called simply fabric login, and obviously, it is important to use NICs that support fabric login in building a SAN.

Another key issue for devices attached to a SAN is the ability to discover all the devices in the switching fabric. Fibre Channel uses Simple Name Service (SNS), a discovery mechanism that learns the address, type, and symbolic name of each device in the switching fabric. SNS information resides in Fibre Channel switches, and NICs and storage controllers request SNS data from the switches. Thus it is advisable to look for Fibre Channel NICs and storage controllers that back SNS.