Interview What does a HW Fibre Channel over Ethernet (FCoE) vendor think of Intel's software FCoE stack? We asked QLogic's Host Solutions Group through Henrik Hansen, its European marketing director.

Intel has released an openly available Fibre Channel over Ethernet (FCoE) software stack so users can send and receive messages to Fibre Channel access storage systems without having to use FCoE converged network adapters (CNAs), specialised Ethernet interface cards with FCoE functions added.

The CNA supplier thinking is, generally, that servers should run applications and offload storage I/O processing to peripheral cards.

So El Reg asked Hansen about QLogic's position on Intel's SW FCoE. We've edited the replies to bring out what we think are the essential points. The resulting Q&A session has some QLogic marketing puffery in it but the general message is clear enough: software FCoE can’t cut it in the data centre.

El Reg: What are the main differences between Intel's open source FCoE software used on a standard Ethernet NIC and QLogic's FCoE-capable CNA?

Henrik Hansen: Host systems using Intel or NICs running FCoE software initiators will be limited in scalability as storage workload processing by the CPU can command up to 70 per cent of the CPU resources, leaving little for application processing or for virtual machines.

A CNA on the other hand offloads FCoE to the adapter and requires between 4-10 per cent of the CPU to process the same storage workloads. FCoE software initiators have limited O/S support (currently Linux only), with Microsoft not yet not commenting on a support time frame, and issues within the way Hypervisors and the O/S exchange protocol processing. The current implementation of SW initiators will not work. Changes must first be made in the SW architecture for hypervisor support.

SW initiators will require years of development and real world deployment before they are ready for enterprise-wide storage deployments: Intel currently only has five vendors qualified while QLogic has over 80 qualified vendors with thousands of products.

We have support for OEM partitioning (HPs Flex-10, IBM's Virtual Fabric Adapter and QLogic’s own, switch-agnostic NPAR (with embedded layer 2 switching)) including QoS to segment networks and improve application performance compared to Intel’s limited VLAN partitioning.

El Reg: The HW CNA vendors say they offer much better management facilities as well. Moving on, what effect do you think Intel's FCOE software will have on the storage networking market?

Henrik Hansen: QLogic does not believe data centre administrators will trust their enterprise storage application to an unproven technology that is receiving limited endorsment by storage manufactures. It will take many years for [Intel's SW FCoE to] receive pervasive storage qualification, OS and hypervisor support. With most of the OEMs supporting proven storage driver stacks, it will in fact stall acceptance of S/W initiators.

El Reg: With multi-core X86 processors do you really need a dedicated FCoE engine on a CNA instead of using a standard Ethernet NIC?

Henrik Hansen: Virtual Machine (VM) density continues to grow, and this will have a material effect on servers attempting to run software initiators and VM’s simultaneously. In order to efficiently scale these servers, CPU [cycles] must be conserved for the hypervisors, and not used for processing storage I/O.

El Reg: As there are now more software iSCSI initiators than iSCSI-capable Ethernet interface card initiators, won't the FCOE market follow iSCSI, with the majority of FC ports on servers being driven by software FCoE code stacks and not CNAs?

Henrik Hansen: iSCSI initiators have mainly been adopted by small to medium business (SMB) where enterprise reliability is not as much of a concern as it is within enterprise storage market.

A new dichotomy is occurring within the data centre; this is being driven by virtualisation and convergence onto one wire. Implementing both with an FCoE software initiator will starve the CPU and limit the scalability of virtual machines as well as throughput requirements for storage-demanding applications.

In order to scale efficiently within this new dichotomy, CPU resource will be better used serving VMs and applications than processing of I/O.

El Reg: Will it be feasible to mix storage networking traffic with general Ethernet traffic?

Henrik Hansen: Without enterprise management applications, CPU-offload and a proven storage driver stack it would be a stretch to believe this could be successful.

El Reg: Will physical Fibre Channel users move to software FCoE initiation and bypass expensive CNAs altogether?

Henrik Hansen: No – enterprise Fibre Channel users will want to retain the reliability that only their existing proven storage stack can offer. Price differentiation may not be as much as you believe, and what you are paying for is piece of mind that your storage infrastructure will work as advertised.

In comparison, with an Intel solution, VM density, and application workload will be sacrificed, which comes with additional expense. The purchase of more CPU or less VMs per physical server will drive up data centre costs above the difference of a NIC compared to a CNA.

El Reg: What effect will 16Gbit/s Fibre Channel (FC) have on this, being faster than 10Gbits Ethernet?

Henrik Hansen: Not all data centres are interested in convergence. Some believe that storage traffic is best separated and managed by storage administrators. These data centres will remain on FC and migrate to 16Gb FC in the future.

El Reg: Has Intel miscalculated what the FC market needs, or has QLogic miscalculated?

Henrik Hansen: The 10Gb Ethernet market is a highly competitive market with many new players as well as large, proven players. QLogic believes that the value of storage over Ethernet is held within the storage driver stack. Many others believe this philosophy is true, including Broadcom who attempted a hostile takeover of Emulex for its driver stack. OEMs seem to hold this same belief as CNAs have won all storage OEM design wins to date.

El Reg: Meaning Intel has miscalculated, at least as as far as the enterprise data centre is concerned, and possibly elsewhere too. What effect will the current situation of FCoE standards have on Intel's SW FCOE chances?

Henrik Hansen: The standards will not drive adoption; O/S certifications, storage qualifications and Hypervisor adoption will, and FCoE software initiators are far behind CNAs with their proven driver stack and support by all fore-mentioned criteria.

Summing up

SW FCoE, if it is taken up, will be taken up by the SMBs, like iSCSI, and not by enterprise data centres. The latter will prefer HW CNAs because they will be certified by OEMS, work with server O/S and hypervisor system software, support OEM partitioning, provide better and easier management and help to keep storage traffic hygienically separated from general LAN traffic.

It may be a bit of a stretch to assert that FCoE standards will not drive adoption. After all, the lack of such standards has been cited as a factor slowing FCoE adoption.

The QLogic takeaway here is that, in the enterprise data centre, Intel's SW FCoE stack won't cut it. The Reg reckons that outside and in SMB land there is existing and proven iSCSI. What need is there therefore, for SW FCoE? What does it offer that iSCSCI does not for the SMB market? ®