White Papers

BP1028 EqualLogic iSCSI for Fibre Channel Professionals 3
3 Fibre Channel and iSCSI basic comparison
The roots of both the FC and iSCSI protocols are the same – SCSI. Both protocols were developed to
improve upon this well-established standard, and to allow it to work with modern hardware
technologies. Whereas SCSI was designed as a parallel, bus architecture, FC and iSCSI both transmit
data serially in frames or packets. FC and iSCSI both encapsulate SCSI commands in these frames or
packets to retain a level of backward compatibility with operating systems and applications that rely on
block-based storage.
Both FC and iSCSI protocols are block-based storage protocols and both allow connection of hosts
and storage devices together, to create a Storage Area Network or SAN. The SAN allows
administrators to more effectively manage and share storage resources between various systems,
instead of creating β€œislands” of storage that are dedicated to a single host.
Figure 1 - Traditional Direct Attach Storage Island
FC has internal mechanisms for automatic addressing and discovery, whereas iSCSI relies on TCP/IP
addressing and iSCSI has its own methods for discovery.
FC requires a dedicated switch fabric (switch or switches) that understands the FC protocol and how
to transport FC frames to and from the target. Host Bus Adapters (HBAs) and storage device ports are
connected to the fabric via approved copper or optical cabling. Today FC supports speeds up to 8
Gb/sec, with plans to increase this speed in future versions.
iSCSI, on the other hand, leverages or builds upon Ethernet and TCP/IP standards –and therefore can
make use of existing 1 Gb/sec and 10 Gb/sec Ethernet hardware technologies. In addition to
dedicated HBAs that support iSCSI offload, many standard Ethernet network interface cards (NICs) can
be used with a software iSCSI initiator to provide the same functionality. However, it is important to
understand that not all Ethernet switches and NICs are created equal, and while most will provide the
basic functionality required for connectivity, not all will provide the performance required. This will be
discussed in more detail later in the paper.