A single protocol in your SAN?

Typical use of the fibre channel is inefficient, and can be made better

A newly proposed standard, dubbed FCoE (Fibre Channel over Ethernet), aims to bring together the efficiency of the FC (Fibre Channel) transport and the ubiquity of Ethernet.

It's no mystery that the majority of storage networks runs on fibre, and FC is the transport protocol that rules data exchanges over that medium. However, the FC fabric is pretty much limited to the storage back end, and corporate data has to jump over the ubiquitous Ethernet to reach local and remote users or to move to a remote SAN, for example.

A typical use of FCoIP (Fibre Channel over IP) is to link remote fabrics, but it can also connect neighbouring SAN islands when merging them is not a viable option. The FCoIP protocol essentially bags each FC frame in a TCP/IP container . At the end of the IP segment, that bag is removed and the original frame is delivered to the FC fabric at the remote site.

Sound inefficient? You bet it is. Can we do better? After listening to Claudio DeSanti, vice chairman of the T11 Committee and technical leader of Cisco's Data Center Business Unit, I think FCoE can.

What FCoE proposes is essentially running FC directly over Ethernet, without using another transport layer (TCP/IP serves as this transport layer for FCoIP). With FCoE, the FC frame is wrapped inside an Ethernet frame, all with minimal overhead as compared to FCoIP.

One of the problems that the new standard has to solve is that it's perfectly acceptable to discard a frame in the Ethernet world, while similar behavior is a mortal sin in FC networks. For example, Ethernet drops frames when the amount of incoming traffic exceeds the capacity of the buffers in a switch. Dropping a frame doesn't cause data loss, because TCP will retransmit frames for which there is no acknowledgement, but that retransmission causes a delay.

By contrast, the obsessively efficient FC protocol never drops a frame. Each end of a FC connection keeps the other party informed of how many buffers are available, and frames are sent only if there is enough buffer capacity at the destination port.

FCoE aims to mimic that behavior via PAUSE frames , a little-known and rarely used extension to the Ethernet protocol that, as its name implies, suspends the flow when there is a congestion point.

It may take years before FCoE products reach our SANs, but I'll speculate that the new standard will make it easier and more affordable to connect your servers to the fabric without doubling with another transport protocol such as iSCSI. You may still need FCoIP to bridge remote fabrics, but local connections can speak FC regardless of the medium.

Is the future of iSCSI threatened by FCoE? It's hard to tell at this point, but I think the usual factors such as cost and friendliness of the solutions will determine the outcome.

Perhaps the most interesting aspect of FCoE is that it will make it possible to consolidate FC and Ethernet into a single, reliable, fast fabric -- 10 Gig Ethernet, anyone?

Join the PC World newsletter!

Error: Please check your email address.

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Mario Apicella

InfoWorld
Show Comments

Essentials

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

Budget

Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?