What is Fibre Channel over Ethernet (FCoE)?

Fibre Channel Over Ethernet (FCoE) is the encapsulation and transmission of Fibre Channel (FC) frames over enhanced Ethernet networks, combining the advantages of Ethernet for information-sharing across a local area network (LAN) and the storage management capabilities of FC as used in a storage area network (SAN). It allows both types of traffic to pass through the same physical cable while preserving the benefits of the FC protocol. Some organizations use FCoE to completely converge their LAN and SAN networks.

For low-end storage, businesses may find iSCSI sufficient; when performance, reliability, and low latency are paramount, an FC SAN is the right choice. FCoE sits somewhere between the two, offering a balance between performance and cost and a way to gradually transition from a traditional and far more expensive FC SAN to more affordable Ethernet-based solutions.

Here’s what you need to know about the FCoE storage technology.

How Does Fibre Channel over Ethernet (FCoE) Work?

FCoE works in a similar way to native Fibre Channel, except it encapsulates FC frames in an Ethernet header instead of an FC header. Storage and data traffic are transmitted from a converged network adapter (CNA), which includes an FC host bus adapter (HBA) and a network interface card (NIC) for TCP/IP Ethernet traffic.

This ability is made possible by enhancements to the IEEE Data Center Bridging standards, which upgrade Ethernet behavior to support input/output (I/O) convergence of LAN and SAN traffic over the same physical Ethernet network infrastructure. This gets around the fact that FC is a lossless protocol that uses buffer-to-buffer credits to ensure frames are not lost. Ethernet lacks this lossless capability, as it relies on other protocols such as TCP for acknowledgments and retransmissions as a way to avoid loss of packets. 

FC frames are never segmented to be sent across multiple Ethernet frames. However, it is important to understand that data traffic still requires a MAC address. This is addressed by virtualizing the physical interface into a virtual NIC with a MAC address for the data traffic and a virtual HBA for storage. Otherwise, FCoE works in exactly the same way as traditional Fibre Channel.

The Importance of Fibre Channel over Ethernet (FCoE)

Ethernet networks are everywhere. They are used in offices, data centers, many homes, and most businesses. Speeds have increased to more than 100 Gbps, with the current roadmap extending to 400 Gbps. It makes sense, therefore, for FC to capitalize on its ubiquitous nature. 

Ethernet enhancements enabling FCoE allowed many large enterprises to use it, and most equipment suppliers and software providers support it. In some cases, such as servers, it’s possible to run FCoE over a standard Ethernet NIC. However, anyone using FCoE usually demands high performance and that is best achieved with a CNA. 

FCoE actually operates at a different layer of the stack than Ethernet, which makes it routable over non-contiguous networks. When used in a SAN, it is much more affordable than strictly FC, as it eliminates the need to buy dedicated FC hardware. Further, the skill needed to run FCoE is more commonly available than that of an FC SAN, which lowers staffing costs and increases reliability.

Fibre Channel over Ethernet Benefits

FCoE offers a number of benefits across a wide range of applications. Here are the most common:

• Cost Reduction—Businesses that want to use FC for storage can use FCoE to gain many of the same advantages of FC at less cost, without having to buy so much dedicated FC hardware. 
• Lack of Technical Skills—Hiring veteran SAN administrators can be difficult and expensive. But FCoE can be administered by professionals experienced with Ethernet and iSCSI with some training.
• Performance Improvements—FCoE offers better performance than iSCI networking, though not equal to strictly FC. Businesses running an iSCI SAN will experience a performance bump by switching to FCoE. 
• SAN Refreshes—Many SANs are reaching end-of-life, and the price tag for upgrading can be steep. Adding Ethernet-based FCoE solutions keeps costs lower, as an Ethernet network is already in place as are NICs, though CNAs may need to be added along with multi-protocol switches. 
• Flexibility—FCoE often adds flexibility to highly virtualized server environments or multi-tenant environments. Workloads and virtual machines (VMs) from the same physical servers may connect to different storage types, made easier by FCoE.

Challenges of FCoE

FCoE has some challenges and limitations for users to be aware of. Here are the most common:

• Network Contention—Running separate FC SAN and Ethernet networks has the advantage of keeping key storage traffic away from the data network. However, FCoE sends storage traffic over the same network as other traffic, which can result in network contention, delays, and bottlenecks.
• Compatibility—FCoE often requires new network adapters and specially designed switches. Some gear can support multiple protocols and run FC and Ethernet traffic simultaneously, but compatibility issues should be considered before purchase. 
• Implementation—As FC SANs have a reputation for complexity, some may underestimate the effort of migrating from FC to FCoE. Careful planning is needed to successfully switch from FC to FCoE.

Bottom Line

If a modern FC SAN network is operating, there is no need to switch to FCoE—but if that infrastructure is aging, augmenting it with FCoE should be on the table. Businesses may consider a slow transition from all-FC to some FCoE by introducing hybrid switches and other gear that supports both. 

FCoE can bring about reduced storage cost and many applications may work well even if network contention is sometimes an issue. But for highest possible storage performance, FC SANs are the best option. Note, though, that FCoE does provide relatively high-speed data transfer in tandem with relatively low latency. It does a good job of bridging the performance gap between FC and Ethernet. FCoE, then, can often deal with demanding workloads. Some even use it successfully for artificial intelligence (AI), real-time data analytics, and high-performance computing (HPC) applications.

Those considering FCoE should evaluate overall performance requirements. FCoE provides higher-speed data transfer and lower latency than traditional iSCSI storage networks. Although FCoE is far cheaper than FC, it still comes at a cost premium compared to a plain and simple iSCSI SAN architecture that can run on commodity hardware. 

Read 5 Types of Enterprise Data Storage to learn more about organizations’ different approaches to retaining and accessing the massive amounts of data they collect and rely on for decision making.