A Fibre Channel Card installed in the XServe and at least one Fibre Channel cable. If your XServe RAID has both controllers populated with drives you'll need two.
You should find these manuals useful?
I guess should have asked which Fibre card to use and which Fibre cables. We would like to use the 4GB cards to be compatible with future technology, if this technology continues. In the manual for the XserveRAID, it mentions 2GB cards however these cards do not use the PCI Express ports that our Early 2008 Xserve uses. My assumtion is that I can get either a dual or quad-channel 4Gb Fibre Channel PCI Express Card and 4Gb fibre cables. From what I've researched, it appears the 4Gb fibre cables are backward compatible with 2Gb and this should work. So this is what I'm really after, will this work? Thanks for your help.