The protocols of choice are Fibre Channel, iSCSI, and NAS (NFS). Your choices are going to be 8Gbyte FC (maybe 4Gbyte), 1Gbyte iSCSI, and 1Gbit/s or possibly 10Gbit/s Ethernet w/ NFS.
When it comes to straight performance, many organizations concede that Fibre has the performance advantage from a raw numbers standpoint. Choosing iSCSI or NFS for ease of use and costs. When it comes to building a storage infrastructure, the decision points are performance, cost, and ease of use.