The current SAN market is clearly divided into two camps; there are those who advocate fibre channel and see it as the “pure” storage networking technology and there are the rebels promoting iSCSI. Both sides believe they own what will become (or remain) the dominant technology.

Personally, I believe in the short term, the storage market will be a bit of both. In large, enterprise-class customers, fibre channel is entrenched and that’s simply because FC was the only choice. These organisations have developed knowledge, processes and procedures which are reaching a level of maturity. In addition, change for change sake is a bad thing, so suggesting the wholesale re-engineering of large and complex storage SANs to new technology is unlikely to be met positively.

On the opposite side, iSCSI is a great alternative for companies who choose not to or can’t afford to invest in fibre channel technology. iSCSI currently also supports certain niche environments such as VMware, offering better VMware server and client support.

No doubt over time even large organisations will see the merits of iSCSI and implement it in a tactical fashion where it is most appropriate. It will be up to consultants (such as myself) to expound the virtues and pitfalls of both technologies.

One thing I think will not happen is that iSCSI will completely replace fibre channel.

The waters are about to become muddied, however by the new upstarts of AoE and FCoE. I think AoE is niche and a curiosity but no more than that. FCoE however, has the backing of some big players, not least of which is Cisco, who clearly want to dominate the datacentre interconnect market.

On the surface, FCoE seems a good play; a technology which provides a single pipe for each server. Reduction in cost and complexity. But datacentres are not that simple. Today we already deploy multiple NICs into servers, perhaps one for front-end access and one for backup, even though this traffic could conceivably all go over the same cable. Why? For the same reason that pedestrians, cyclists and cars are given their own “highway”; they are different types of traffic and they don’t mix well.

I think we will see the same with FCoE implementations. There are many places where bottlenecks can and will occur; the I/O stack, the IP stack, the CNA buffer stack, the FCoE switch port, the FCoE ISL and so on. Cisco are already talking about technologies to mitigate these problems, but the plain fact is that large SANs (and IP networks) benefit from physical segregation where the economies of scale permit discrete physical fabrics and LANs. Storage Architects will continue to design to these principles as a way of guaranteeing performance rather than trust the performance and congestion features.

It is also worth noting that FCoE technology is not coming in as a cheap alternative to fibre channel. CNA cards will be as expensive as HBA cards and the question has to be asked as to why today’s HBA vendors would cannibalise their own market by selling a direct HBA replacement at lower cost.

What about the long term future? I think the “physical pipe” part of the infrastructure will over time move to support the FC, IP and FCoE standards from a single fibre connection. This will implicitly also support iSCSI and iSCSI initiators will become a ubiquitous part of the O/S. This will happen not merely because a single connection can be used per server, but because commoditisation of the interconnect dictates that it will be easier to create a single HBA/CNA ASIC which supports all the protocols, much in the same way as DVD drives today support CD-R, CD+R, CD-RW, DVD-R, etc. Customers will choose whether they feel comfortable with a single or multiple physical connections as part of their infrastructure design.

And for iSCSI? Clearly iSCSI has a niche while NICs are substantially cheaper than CNAs and HBAs, however if prices drop to a level where using a CNA is a no cost alternative, then iSCSI has a rocky future unless it can find new ways to differentiate itself.