Lock-in or escape
There are two ways to extend access to Fibre Channel storage area networks (FC SANs) to servers without FC host bus adapters (HBAs): Fibre Channel over Ethernet (FCoE); or iSCSI. Both use Ethernet as the transport medium but one locks you in to Fibre Channel and the other provides an escape route.
With iSCSI, SCSI storage commands and data are wrapped up inside TCP/IP data packets and sent across Ethernet to a storage resource. This could be a pure IP SAN, such as those from Dell/EqualLogic and LeftHand Networks or it could be a Fibre Channel SAN via an iSCSI port on an intervening FC fabric switch or director.