The Fibre Channel SAN Fabric

Fibre Channel is the power behind the SAN. Fibre Channel allows for an active intelligent interconnection scheme, called a fabric, to connect devices. In the context of a storage area network (SAN), the fabric typically refers to the detailed makeup of the network, such as cards and attached devices. The most common SAN fabrics include Fibre Channel switched, switched Small Computer System Interface (SCSI), and switched Serial Storage Architecture (SSA). Generally, SAN interconnects are connected to Fibre Channel switches. Switches allow many advantages in building centralized, centrally managed, and consolidated storage repositories shared across a number of applications. The switches furnish the backbone for all the connected devices, with one or more of the switches acting as a Fibre Channel switching fabric. SAN switch fabrics allow attachments of thousands of nodes. Although SAN fabrics are often mixed together, it should be remembered that they are really distinct elements of the SAN.

Fibre Channel architecture offers several topologies for network design, primarily point-to-point, arbitrated loop, and switch. The ports in a point-to-point connection are called N_Ports, loop connections are called NL_Ports, and a Fibre Channel switch or network of switches is called a fabric. All are based on gigabit speeds, with effective 100 MBps throughput (200 MB full duplex). All allow for both copper and fiberoptic cable plant, with maximum distances appropriate to the media (30 m for copper, 500 m for short-wave laser over multimode fiber,...