Fibre Channel Advantages and disadvantages of using a SAN

Fibre Channel switch (FC switch)

A Fibre Channel switch is a networking device that is compatible with the FC protocol and designed for use in a dedicated storage area network (SAN).

An FC switch inspects a data packet header, determines the computing devices of origin and destination and forwards the packet to the intended system. FC switches come in different types including modular director switches, also known as backbone switches, with a high port count and fixed-port or semi-modular switches, also known as edge switches. FC switches can be combined to create large SAN fabrics that interconnect thousands of servers and storage ports.

An FC switch is designed for high-performance, low-latency, high-availability and lossless data transmission. Director-class FC switches can add capabilities, such as encryption and zoning, to disable unwanted traffic.

How a Fibre Channel switch works

As previously noted, FC networks are specifically designed to connect hosts, or servers, to storage devices. This can be accomplished without the use of an FC switch. FC supports point-to-point connections in which a server's FC host bus adapter is physically connected directly to a storage device, thereby allowing the host to access the attached storage directly. Although a point-to-point architecture might be desirable in certain situations, the architecture doesn't scale well, because every host would require a direct connection to any storage device that it could conceivably need to access.

Fibre Channel topologies
Each interconnection type in the switched fabric topology requires a different number of Fibre Channel switches.

An FC switch addresses this problem by acting as an intermediary between servers and storage. Servers are provided with a physical link to an FC switch, rather than being attached directly to storage devices. Likewise, storage devices are also attached to the switch. When a server needs to access a storage device, the FC switch directs the request to the appropriate storage device.

Benefits of a Fibre Channel switch

  • Direct connections aren't required. An FC switch eliminates the need for every server to have a dedicated connection to every storage array. Essentially, an FC switch reduces complexity.
  • Greater transmission speed. In some cases, an FC switch can enable greater bandwidth than can be achieved through a single FC connection. This is because FC switches can handle parallel traffic streams, and so the total bandwidth provided by an FC switch is usually greater than what any one single port can deliver.

Fibre Channel switches vs. other network switches

Although there are some similarities between FC switches and other types of network switches, there are also points of differentiation. Most network switches are designed for use on Ethernet networks. They allow a huge variety of devices to communicate with one another using Ethernet packets. An Ethernet network can accommodate devices such as PCs (personal computers), tablets and IoT (internet of things) devices.

FC switches, on the other hand, are used only for connecting servers to storage arrays. They aren't used for general-purpose network communications, nor do FC devices require an IP (Internet Protocol) address.

Another important difference is that FC is a lossless protocol, whereas packet loss is possible on an Ethernet network. FC also ensures that packets arrive in the order in which they were transmitted, whereas Ethernet networks allow packets to arrive in a different order from the way they were transmitted.

This was last updated in September 2020

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