By Bill Robbins
—Since Fibre Channel over Ethernet (FCoE) was first proposed as a standard nearly a year ago by a collection of network storage vendors, the noise surrounding the technology has been deafening. Touted as the next-generation networking and storage technology, FCoE is an elixir for data centers that suffer from excessive power consumption, cabling nightmares, and spiraling costs. Yet, the people who will likely benefit the most from FCoE may be the roadblocks to adoption of the standard.
FCoE is a convergence of two enterprise technologies—Ethernet networking and storage—through a single unified fabric that allows Fibre Channel storage traffic to move across high-speed Ethernet infrastructures after some modification. As such, the reach and capabilities of SANs are extended while protecting existing investments in storage networks.
The ANSI T11 standards committee received the proposal to review FCoE in April 2007. ANSI is also evaluating proposals that will make Ethernet a "lossless" technology capable of supporting Fibre Channel traffic (see Sidebar 1). FCoE network switches and Converged Network Adapters (CNAs) were announced by vendors such as Cisco, Emulex, and QLogic this Spring. And the modifications to the Ethernet standard, as well as the FCoE standard, are expected to be finalized before year-end.
But as many companies begin to put their toe in the FCoE water, some are beginning to see potential organizational conflicts that would potentially slow implementation.
"The challenge is bringing two organizations—the networking team and the storage team, together that in the past have been typically siloed," says Joe Gervais, senior director of marketing for Emulex. "We're talking convergence, so it's going to take a lot more cooperation than what we've seen in the past with these two groups. Convergence isn't hinged on technology, but on a mindset of organizations coming together."
FCoE is also challenged with a variety of moving parts within the industry that will have to come together. The FCoE ecosystem is expansive, with a variety of vendors in the storage, adapter, and switch markets. No one vendor can bring the technology to market by simply voicing support or by delivering a single component. Industry analysts say it will take a multi-vendor solutions to bring FCoE into a complete infrastructure play.
However, FCoE provides a carrot for both vendors and data-center managers. Chief among the benefits is the consolidation of rack space. By increasing network bandwidth through consolidation into fewer servers, FCoE begins to free up space in the data center. With the reduction in servers and the introduction of CNAs that replace the myriad of Fibre Channel host bus adapters, Gigabit Ethernet network adapters, and server interconnect adapters, comes a reduction of cabling. In some cases, FCoE is expected to reduce the number of networks from three to one over time, providing more computing power in a smaller footprint. Fewer servers mean fewer cables and less energy consumption, which leads to "green" data centers.
Deepak Munjal, Cisco's manager of data-center marketing, says the green computing aspect of FCoE is based less on environmental concerns but on the reality of limited power supplies. "The amount of power coming from our utility companies is obviously not limitless," says Munjal. "We're seeing customers growing increasingly concerned about running out of power. So anything they can do to reduce power by simplifying and consolidating their networks will allow them to make better use of the power they have."
Beyond the issues of cabling and energy consumption, data-center managers will likely gravitate to FCoE because of its ability to protect existing investments in servers and network infrastructure. FCoE promises seamless integration with existing Fibre Channel and iSCSI storage devices. With CNAs offered by Emulex, QLogic, and others, the technology is provided for both IP and Fibre Channel.
"The beauty of FCoE is that customers can use all of their existing Fibre Channel storage products from any vendor, and when deploying new servers they can use the CNAs and still be able to connect to their existing Fibre Channel storage," says Amit Vashi, vice president of marketing for QLogic's Host Solutions Group.
Vashi says FCoE further advances the cause of investment protection with common operating system drivers and applications. SAN management software, for example, is able to work the same way it does now, but with greater performance, simplified management, and easier integration with Ethernet technology.
Despite expectations by users and vendors, FCoE adoption will depend largely on how quickly large enterprises will take the plunge and how quickly others will follow. If the economy slips further into a recession, then it is possible that data-center managers will want to play it safe and avoid new technologies such as FCoE, regardless of its promises. To date, there are no large-scale FCoE deployments.
However, Munjal notes that demand is growing for a simplified, converged network environment and for lower energy costs. "The only question is what technology will take us there. The next six months are going to be very telling as customers adopt this technology."
Bill Robbins is research manager with Storage Strategies NOW, in Austin, TX. He can be contacted at brobbins (at) ssg-now.com.
Making Ethernet a 'lossless' protocol
Implementing Fibre Channel over Ethernet (FCoE) makes a lot of sense, especially if the Ethernet protocol is enhanced with some new features.
Because Ethernet deals with congestion by dropping packets—an occurrence that would not be tolerated in Fibre Channel environments—the Ethernet protocol needs to be enhanced to make it a "lossless" protocol.
Vendors working through the ANSI and IEEE standards organizations have proposed a number of modifications to the Ethernet protocol. These changes alleviate the latency of a congested network and ensure Fibre Channel packets make it through to their destination in the order intended.
The changes to the Ethernet protocol are termed Converged Enhanced Ethernet (CEE) and include Per Priority PAUSE, congestion management (CM), CM discovery and capability exchange, and priority processing/packet scheduling.
- Per priority PAUSE provides a mechanism at the congestion point to support differentiated services and to minimize or eliminate the dropping of packets due to congestion;
- CM and CM discovery and capability exchange—Two modifications to the 802.1 specification will provide link-level congestion management for unicast traffic in networks with long-lived data flows with respect to bandwidth-delayed products. The end-to-end congestion management enhancement—802.1Qau—provides for the throttling of end stations when congestion occurs in the network, thus relieving congestion. CM discovery and capability exchange provide a mechanism to define the domain formed by CM-compliant bridges and end stations to ensure interoperability. Another enhancement—P802.3ar—specifies a mechanism to support the communication of congestion information and limit the rate of transmitted data on an Ethernet link, while preserving existing Media Access Control/Physical Layer Signaling (MAC/PLS) service interfaces;
- Priority processing/packet scheduling provides for classes of traffic with differentiated service so that high-priority traffic gets priority in transmission in end stations and switches.
These enhancements, which should be ratified by year-end, are the secret sauce that will enable Fibre Channel traffic to run over Ethernet.
Adoption of FCoE won't happen overnight; it will occur in stages.
Figure 1 shows a typical scenario prior to the use of Converged Network Adapters (CNAs). A server that is attached to the network, storage, and other servers may contain as many as six network adapters, host bus adapters (HBAs), and host channel adapters (HCAs). By replacing these adapters with a CNA from vendors such as Emulex or QLogic, IT administrators can not only reduce the number of adapters in the server, but also the amount of cabling necessary to wire the infrastructure, as shown in Figure 2.
Users will also adopt switches such as Brocade's new 'Top of the Rack' switch that has FCoE capability as a bridge to full convergence (see Figure 3). This method of deployment will preserve existing Fibre Channel, Ethernet, and InfiniBand investments.