Growth is one of the most difficult challenges facing storage managers with Fibre Channel (FC) SANs because the FC protocol, by design, sacrificed scalability for speed. The Internet Protocol (IP) and the Ethernet network offer scalability that two variations of the FC protocol--iFCP and FCIP--use to connect SAN islands and overcome FC networking limitations. Unfortunately, each switch vendor supports only a proprietary version of iFCP or FCIP (see What switches support which protocol, this page). Storage managers need to understand the high-level differences between these two protocols to make better decisions on which protocol/switch best fits their SAN infrastructure and expansion needs.
Typically, SAN growth problems arise in one of two ways. Storage managers with small- and medium-sized SANs tend to create SAN islands to overcome scaling issues, but continued growth increases management complexity. Storage managers with large SANs have successfully implemented director-class switches, but they must now connect their large SAN to a secondary data center SAN at a remote site because of new disaster recovery requirements. Each of these growth challenges can be solved by connecting separate FC SANs over a TCP/IP network.
At a basic level, the iFCP and FCIP protocols connect separate FC SANs by encapsulating FC frames within TCP packets and using the LAN/WAN infrastructure as the transport layer. A storage manager should expect that either protocol will:
- Scale to connect multiple SAN islands or multiple data centers.
- Provide resiliency and recovery from LAN/WAN failures.
But the Internet--and IP--don't expect the same level of component reliability that is taken for granted in FC SANs. A server can appear and disappear on an Ethernet network using IP without disruption unless it was actively receiving or transmitting data; even then, only the clients at the other side of the data flows are likely to notice. The loss of a node on an FC SAN, however, will result in state change notifications because the FC SAN assumes longevity in connection states. For this reason, resiliency and recovery are important to the storage manager because while the LAN/WAN may be stateless, FC SANs aren't.
