Fibre Channel

Fibre Channel – often referred to as FC, is and has been the main infrastructure and protocol used in the storage networking industry since the mid 1990s.  Its high speed (multi-gigabit) data rate has been enhanced over the years, allowing up to about 8 gigabits per second today, and twice that rate in the near future.

Not Necessarily Fiber-Optics

One of the biggest misconceptions is that Fibre Channel exclusively used fiber optic cables, or links.  While it is true that long distance runs will be carried over optical links, many FC disk enclosures carry the signals over copper cables, or traces on a backplane.  Obviously there has to be somewhere that the conversion takes place between optics and copper, and a very common component that does this is the GBIC (GigaBit Interface Converter).

Topologies

There are three basic topologies used with Fibre Channel.  These are point-to-point, Arbitrated Loop, and Switched Fabric.

Point-to-point is the simplest, and is exactly what it sound like, where two devices, or nodes, are connected directly together.

Arbitrated Loop is when a series of device are connected in a ring, or loop.  This allows multiple devices to be connected and available for use.  This is a very common configuration for a JBOD (Just a Bunch of Disks) type enclosure.  A limitation of this configuration is that only two node can use the loop at any given time.

Switched Fabric is the most common topology used in enterprise class storage system.  This means that a Fibre Channel Switch will be used to connect multiple devices and adds the capability of having multiple communications occurring at that same time.  The more ports you have on the switch, the more simultaneous communications you can have.  Of course this increases the cost and complexity of the system, but you don’t get high speed simultaneous data flow for free.

There is much more to Fibre Channel than what will fit in a single glossary post, but I will try to add more in the future.  Please let a comment if you have specific questions.

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