Storage Interfaces

Fibre Channel Components

In order for Fibre Channel devices to interact with other devices, certain components must be in place to facilitate communication. Here are some of the most common:

Host Bus Adapers

Host Bus Adapters (HBAs) perform a similar function to SCSI controllers. They are installed in a server and connect the server to Fibre Channel devices.

Cables

The two main categories of Fibre cables are copper and optical. Optical cables provide no benefit in speed over copper cables; however, they are not as prone to electromagnetic interference (EMI) or cross talk as are copper cables. This gives optical cables an advantage in usable length.
Among optical cables, there is a further distinction that also relates to distance- single mode vs. multimode. Single mode cables only allow one beam of light to occupy the cable at any given time. Multimode cables, which are more common than single mode cables, permit multiple beams to enter the cable, which can lead to chromatic dispersion. The practical implication of this is that usable multimode cable lengths are limited to several hundred meters, while single mode cables may cover much greater distances (kilometers) with no signal problems.

Connectors

A connector is the part of a cable that plugs into a port or an interface. Fibre Channel is a serial interface requiring serial connectors. For copper cables, four different connectors are available. DB-9 and high-speed serial data connectors (HSSDC) are commonly used today. Optical cables use SC cable connectors. One side of the connector is used for transmitting, while the other is used for receiving data.

Generally speaking, in Fibre Channel-2 implementations, 2-GBit HBAs require optical cables with a special Lucent Connector (LC). The LC connector is about half the size of the SC connector.

Switches

Switches are used to provide the connection point between servers and storage devices. Fibre Channel switches usually have 8, 16, 32, or 64 ports, allowing for tremendous scalability. Switches are responsible for directing the flow of data in more complex (switched fabric) topologies. A SAN with multiple switches can have multiple fabrics, which in turn provides redundancy.

GBICs

Gigabit Interface Converters (GBICs) are hot-swappable transceivers used to convert electric currents into to optical signals (and vice versa). GBICs are plugged into switches, allowing copper or Fibre cables to be connected to different types of Fibre Channel devices.

Bridges

Bridges are used to connect non-Fibre Channel devices to Fibre Channel connections. For example, a SCSI-to-Fibre Channel bridge would need to be used to connect a SCSI tape drive to a Fibre Channel device.
Some devices (for example the PowerVault 128T autoloader and 136T tape library) contain integrated bridges so they may easily be connected via Fibre Channel. Stand alone bridges such as the PowerVault 35F must be used to connect non-Fibre Channel devices that do not incorporate integrated bridges.