8Gbps FC.... why?

Early this summer, the FibreChannel Industry Association approved signaling standards for an 8Gbps version of the FibreChannel protocol. 8GBps FC switch and HBA products are expected to arrive in early 2008 in test samples, with major shipments by mid-year. What makes this interesting is, for the first time vendors are delivering their wares before disk products are announced! At this time, Seagate and Hitachi have not announced when or if they will ship 8Gbps disks. Why does that matter?

For the first time, we might see infrastructures that are effectively faster than the backing store. In our current generation, we can claim "end-to-end throughput" - 4Gbps disks attached to 4Gbps arrays on 4Gbps switches and so on. Now, that may no longer be true. Worse yet, there's no evidence to support the believe that the current generation of server hardware can effectively leverage the 8Gbps "pipe". This argument was raised with 10Gbps network cards and iSCSI interfaces, but card vendors claim the protocol overhead prevents the server from obtaining full line-rate. As 10Gbps networking prices fall, it looks like iSCSI can finally provide both lower costs and higher performance than FC.

Infiniband, too, is making inroads across the board. Once relegated only to HPC deployments, it is quickly becoming a common storage interconnect. Scalable storage clusters from DataDirect and Isilon use IB for storage-to-storage and storage-to-host interconnects. If pricing models improve, IB will greatly outstrip both the cost and performance of FC.

8Gbps FC comes to market as virtualization is poised for a meteoric rise; some expect it to become the dominating "operating system' in the data center. Does 8Gbps FC enable virtualization? No more than 2Gbps or 4Gbps. The claims that 8Gbps reduces the number of ISL links between switches may hold true, but it's too early to tell what benefit that really holds.

So the big question I'm left with is why do we need 8Gbps FC? Aside from the ISL argument, there are no drives available (or currently scheduled) and Infiniband and 10Gbps FC offer more bandwidth. Maybe it's finally time for FC to go the way of SCSI and IDE.