What is Fibre Channel over Ethernet?
Fibre Channel over Ethernet (FCoE) is the next evolution of the Fibre Channel networking and Small Computer System Interface (SCSI) block storage connectivity model.
FCoE maps Fibre Channel onto Layer 2 Ethernet, allowing the combination of LAN and SAN traffic onto a link and enabling SAN users to take advantage of the economy of scale, robust vendor community and roadmap of Ethernet.
The combination of LAN and SAN traffic on a link is called unified fabric. Unified fabric eliminates adaptors, cables and devices, resulting in savings that can extend the life of the data centre. FCoE enhances server virtualisation initiatives with the availability of standard server I/O, which supports the LAN and all forms of Ethernet-based storage networking, eliminating specialised networks from the data centre.
FCoE is an industry standard developed by the same standards body that creates and maintains all Fibre Channel standards.
FCoE is specified under INCITS as FC-BB-5. FCoE is complemented by new facilities in Layer 2 Ethernet called Data Centre Bridging (DCB). DCB is a collection of IEEE 802.1 standard enhancements that allows the LAN behaviour of dropping packets upon congestion to co-exist with the SAN requirement of no loss of frames. Classes of service (CoSs) allow this behaviour, and new bandwidth management tools enforce appropriate use of bandwidth among the classes. In this way,
LAN scaling and the deterministic needs of SAN I/O are made compatible.
Why is FCoE Evolutionary?
To implement FCoE and unified fabric, at least two devices are required: a lossless Ethernet switch that can forward Fibre Channel frames and a multifunction server adapter that supports the LAN and SAN. Various switch manufacturers offer FCoE and unified fabric capability such as Brocade, CISCO, HP and Extreme Networks.
For Example, the Cisco Nexus 5000 Series / 7000 series consists of lossless, line-rate 10 Gigabit Ethernet switches that optionally support FCoE and unified fabric on every port. To integrate with installed SANs, native Fibre Channel ports are available for connection to Fibre Channel storage, Fibre Channel host bus adaptors (HBAs), and Fibre Channel switches. The foundation of the Cisco Nexus 5000 Series as true 10 Gigabit Ethernet LAN switches allows them to be deployed across a data centre’s access layer for all purposes.
A powerful new feature of FCoE networks is support for Ethernet pass-through switches. An Ethernet pass-through switch forwards Fibre Channel frames as an upper layer protocol. These switches must be lossless, but they require no knowledge of Fibre Channel technology as long as an FCoE-aware switch exists upstream in the I/O flow.
Thus, specialized Fibre Channel networks can begin to match the economics of Layer 2 Ethernet networks.
Converged network adapters (CNAs) support both LAN plus SCSI and Fibre Channel operating system stacks and can place 10 Gigabit Ethernet LAN and FCoE traffic on the network wire. A CNA can function as just a LAN network controller or a network interface card (NIC) but also have the additional capability of FCoE.
A 10 Gigabit Ethernet CNA typically replaces multiple adapters per server and generally simplifies server physical I/O requirements. Fibre Channel HBA industry leaders QLogic and Emulex market CNAs, with NIC volume leaders preparing offerings for the future. CNA market participation shows how unified fabric and FCoE together provide more competitive choices to users. Implementing FCoE today switches enable unified fabric solutions at the server access layer, typically as top-of-rack (ToR) switches.
Future availability of distribution and core switches with FCoE line cards and storage devices with FCoE interfaces will allow implementation of FCoE fabrics above the access layer and across the network. However, there are powerful benefits to implementing FCoE at the access layer and scaling horizontally with the deployment of servers.
Reduction in the number of adapters and network infrastructure devices:
- Reduction in the number of cables
- Allows economical blend of inexpensive copper and longer-link optical technologies
- Reduces cable installation expenses
- Significantly reduces the number of long cables
- Can increase server density if server deployment is impeded by cable bulk or airflow concerns
- Reduces the possibility of air dams in the data center
- Reduces the possibility of air dams in the data center
- Reduces cable maintenance and provisioning concerns in the data center
- Reduction in the amount of power used
- Reduction in space used due to switch equipment rack occupancy
- Reduction is server height due to fewer add-in card slot requirements if servers are I/O bound
- Redeployment of power and space savings to provisioning of additional servers, extending the life of the data center
Following are typical methods of implementing FCoE and unified fabric:
For larger networks, fully implement I/O consolidation of the LAN, network-attached storage (NAS), and SAN at the access layer, and scale with server deployment. I/O above the access layer either continues as specialized networks or is further consolidated over Ethernet at a later time when modular switch technology is ready.
For smaller networks, implement a full unified fabric network switch, and direct attach either native Fibre Channel or FCoE storage devices to this switch
Consolidate storage networks only over 10 Gigabit Ethernet. This implementation would include iSCSI and FCoE block attached storage (SAN) as well Common Internet File System (CIFS) and Network File System (NFS) file attached storage(NAS). The LAN is left unconsolidated. FCoE is the last and missing element in a unified storage network strategy. Incorporation of the LAN can optionally occur in a later deployment.
Implement FCoE-ready technology at the access layer and migrate to unified fabric at a later date.