"You will see iSCSI in enterprises, especially for replication solutions and for remote office installations," says Steven Scully, research manager for Continuity, Disaster Recovery and Storage Orchestration at IDC. "At the core, those customers will be the big FCoE users. On the other hand, you probably won't find much FCoE in SMB customers."

Since it runs over TCP/IP, iSCSI is susceptible to TCP "overhead," such as the windowing characteristic in TCP, Chapman says. A TCP window is a chunk of data, made up of several packets, sent by a server. After the server receives an acknowledgment from the client that the window has been received -- without errors -- it will send the next window of packets.

If errors occur, the data must be resent. This whole event can introduce latency and packet loss with iSCSI, Chapman says. But nothing precludes a business from converging or unifying servers, storage and networking in a data center with iSCSI -- indeed, Cisco says its can transport iSCSI over Ethernet just as capably as FibreChannel over Ethernet.

And 10Gbps iSCSI converged network adapters are appearing on the market from Network Interface Card vendors such as .

Yet FCoE garners most of the hype and press coverage because of Cisco's emphatic endorsement of the technology for unifying data centers -- and because it's newer than iSCSI. FCoE was standardized less than a year ago while iSCSI is at least 10 years old.