Both Fibre Channel and iSCSI use SCSI commands, the only difference is the media. There are a few more tasks that need to be done with FC vs iSCSI but the basic rules still apply. Currently FC connections have 4x more bandwidth than typical iSCSI (4Gb vs 1Gb). But 10Gb ethernet is starting to roll out. 8Gb FC is starting to come out as well. There is a little more overhead with iSCSI vs FC so iSCSI adds about 1-3ms overhead on latency. Another technology that is starting to roll out is FCOE (Fibre Channel over Ethernet). It's Fibre Channel protocol over ethernet media. It should provide the cost benefits of ethernet without the overhead of iSCSI.