iSCSI dodges Fibre Channel over Ethernet noose

Storage Expo Fibre Channel over Ethernet may not have taken off yet, but at least it's on the taxiway. That's thanks to NetApp's launch of the first native FCoE storage subsystem, converged network adapters (CNAs) from Emulex and QLogic, and Cisco's announcement of the first FCoE switch - the Connectrix NEX-5020, which is based on its Nexus 5000 datacentre switch and can bridge from FCoE to real Fibre Channel.

It means that the new SAN spec - a working draft is now up for ballot - has gone from being just a proposal to something that really works, claimed NetApp marketing manager John Rollason.

FCoE is kind of a grown-up iSCSI for large enterprises - for people who already use Fibre Channel and don't trust the kind of noddy TCP/IP-based technology used by small businesses. The hope of all concerned is that Fibre Channel users will adopt FCoE as a way of connecting extra servers to the SAN via Ethernet.

The interesting thing is that all the companies involved denied that FCoE poses any threat to iSCSI - even though readers with long memories will recall that attaching extra servers to the SAN via Ethernet was one of the ecological niches that iSCSI was originally punted at.

For example, Rollason argued that the two will co-exist, with FCoE filling the SAN extension role that iSCSI failed to snag, and iSCSI being the technology of choice for organisations that don't actually have a SAN yet.

"Today if they're starting from scratch, most people would go iSCSI," he said, adding that he isn't worried if FCoE only appeals to existing Fibre Channel customers. "The vast majority of high-end users - 98 to 99 per cent of the top storage spenders out there - are Fibre Channel. It's not an issue."

Emulex's European marketing director Jason Phippen agreed, but explained it differently. Both enable you to build a converged network, he said, but where iSCSI brings SANs to those who only know Ethernet, FCoE does the opposite, taking Ethernet to those who already know how to build and run datacentre-quality SANs.

The challenge, of course, is that FCoE still requires an expensive new network adapter, albeit one that appears to its host as both a Gigabit Ethernet NIC and a Fibre Channel HBA - the latter complete with zoning, N-port virtualisation and so on.

It also needs new FCoE-capable switches able to prioritise across multiple flows and pause them independently - and it needs a 10Gigabit Ethernet infrastructure. That's because a CNA such as the QLogic 8000 is in effect multiplexing two 4Gbit/s FC ports and two Gigabit Ethernets onto a single network connection, explained Steve Perkins, QLogic's senior systems engineer.

But while all that cost gives the iSCSI boosters plenty of ammunition, Fibre Channel users have invested a lot in their SANs - and FCoE could give that investment a new lease of life, said Jason Phippen.

"We have over a hundred trial FCoE deployments," he said. "They like Fibre Channel and don't intend to move away from it, and they see FCoE as a method of extending it." ®