FCoE (Fibre Channel over Ethernet)
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Posted by: Margaret Rouse
Contributor(s): Brien Posey
FCoE (Fibre Channel over Ethernet) is a storage protocol that enables Fibre Channel (FC) communications to run directly over Ethernet. FCoE makes it possible to move Fibre Channel traffic across existing high-speed Ethernet infrastructure and converges storage and IP protocols onto a single cable transport and interface.
The goal of FCoE is to consolidate I/O (input/output) and reduce switch complexity, as well as to cut back on cable and interface card counts. Adoption of FCoE has been slow, however, due to a scarcity of end-to-end FCoE devices and a reluctance on the part of many organizations to change the way they implement and manage their networks.
Traditionally, organizations have used Ethernet for Transmission Control Protocol/Internet Protocol (TCP/IP) networks and FC for storage networks. Fibre Channel supports high-speed data connections between computing devices that interconnect servers with shared storage devices and between storage controllers and drives. FCoE shares Fibre Channel and Ethernet traffic on the same physical cable or lets organizations separate Fibre Channel and Ethernet traffic on the same hardware.
FCoE uses a lossless Ethernet fabric and its own frame format. It retains Fibre Channel’s device communications but substitutes high-speed Ethernet links for Fibre Channel links between devices.
FCoE works with standard Ethernet cards, cables and switches to handle Fibre Channel traffic at the data link layer, using Ethernet frames to encapsulate, route and transport FC frames across an Ethernet network from one switch with Fibre Channel ports and attached devices to another, similarly equipped switch.
FCoE is often compared to iSCSI (Internet Small Computer System Interface), an IP-based storage networking standard.
How Fibre Channel over Ethernet works
As previously noted, FCoE works by sending Fibre Channel packets across an Ethernet network. It accomplishes this by encapsulating the native Fibre Channel packets inside of Ethernet packets.
To make this work, a special type of network adapter called a converged network adapter — also known as CAN or C-NIC — is used. A converged network adapter is a special type of network adapter that combines the functionality of a Fibre Channel host bus adapter with that of an Ethernet network adapter.
This converged adapter not only provides the required physical connectivity, but it also enables lossless Ethernet. This is essential because Fibre Channel is a lossless protocol, and storage area networks (SANs) expect lossless communications.
Benefits of Fibre Channel over Ethernet
There are several benefits to using Fibre Channel Over Ethernet, including:
- Reduced complexity. Because storage-related traffic is being sent over a conventional Ethernet network, it eliminates the need for Fibre Channel switches. This, in turn, reduces both the architectural complexity and costs.
- Increased performance. Fibre Channel is a high-speed storage protocol, with some storage devices supporting speeds of up to 128 Gbps (gigabits per second). Even so, such devices tend to be expensive. As such, there are many organizations that still use 8 Gbps storage devices and SANs. FCoE makes it possible for such an organization to achieve higher speeds such as 10 Gbps or 40 Gbps by using comparatively inexpensive Ethernet networks.
- Simplified network management. Countless tools exist for managing and monitoring Ethernet networks. Because FCoE routes storage traffic across a standard Ethernet network, an organization might be able to use its existing networking tools to manage storage traffic.
FCoE use cases
- Driving down costs. The main use case for FCOE is driving down costs. FCoE can eliminate the need for costly Fibre Channel switches. Organizations might also reduce costs in the form of power and cooling and from simplified management.
- Legacy hardware. Another use case is that if an organization is using legacy Fibre Channel hardware, it might be able to use FCoE to improve performance without having to invest in modern Fibre Channel hardware.
FCoE vs. other storage protocols
FCoE has a lot of similarities to the iSCSI protocol. Whereas FCoE encapsulates native Fibre Channel packets inside of Ethernet packets, iSCSI encapsulates native SCSI commands inside of IP packets. One major difference between these two protocols is that FCoE is designed to allow Fibre Channel communications across a high-speed Ethernet network and is generally used within the confines of a data center.
On the other hand, iSCSI can be used for communications between devices within a data center, but it is more often used as a means of connecting to a remote storage device. Additionally, FCoE requires a converged network adapter, while iSCSI can be used with any standard NIC.
