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Copper-based Cabling in SANs
When copper cables and copper-based Fibre Channel devices are used in a SAN, we attach them to other Fibre Channel devices using two types of connectors, Copper Gigabit Interface Connectors (GBICs) and Media Interface Adapters (MIAs). Copper GBICs are hot pluggable connectors that attach to Fibre Channel devices using either a DB-9 or the High Speed Serial Data Connector (HSSDC). Shown below are examples of copper GBICs and the associated connector type.
There are two different types of copper GBIC connectors, each with a unique purpose. The first type is the intracabinet GBIC, which as you might have guessed, is used to connect devices located within a cabinet. Intracabinet GBICs are used when you need to connect Fibre Channel devices close together, typically no more than 13 meters apart. Intracabinet GBICs are considered passive devices, as they do not regenerate transmitted signals; they simply pass the signal from one device to another.
The second type of GBIC connector is the intercabinet GBIC. Intercabinet GBICs are used to connect devices that stretch beyond 13 meters and are considered active devices, as they are capable of regenerating a signal before it is passed. In addition, intercabinet GBICs are able to detect and report signal loss and transmission errors. As you might expect, the increased abilities of the intercabinet GBICs add to their cost, making them much more expensive than their intracabinet counterparts.
The second type of connector used to connect copper cables to Fibre Channel devices is the Media Interface Adapter (MIA). There are two key functions of the MIA connector. The first is to attach Fibre Channel devices with a copper interface to optical fiber links. Essentially, MIAs convert a Fibre Channel copper interface to an optical one. The second function of the MIA is to extend the distance of a Fibre Channel link. MIAs can only be attached to Fibre Channel devices using the DB-9 connector and do not support the HSSDC connector type. Shown below is an example of an MIA connector.
Copper vs. Fiber in SANs
Implementing copper is certainly cheaper and perhaps easier than fiber; however, copper-based cable cannot match fiber cable in terms of speed, error free transmissions, and security. Because of these reasons, fiber cable has emerged as the media of choice for storage networks, with copper media filling where it can. In the next Storage Basics article, we'll take a closer look at implementing fiber optic cable in SANs.