Fibre Channel Addressing and Routing Routing and FSPF
• All frames in an Exchange must follow the same path. In addition, all subsequent Exchanges will use the same path unless the paths are recomputed—which generally only happens when the ISL configuration changes.
All of this is according to the FC specification. However, some switch vendors do implement per-exchange or per-frame load-balancing using proprietary protocols.
In addition, some storage array vendors and storage software manufacturers do offer software-based load balancing at the per-exchange or per-frame. Some HBA manufacturers are also beginning to offer load balancing which operates at the HBA driver level. This type of load balancing is performed only with data traffic between servers and storage devices that both have load balancing capability; it is not a fabric-wide capability.