Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building an Extended Distance Cluster Using MC/ServiceGuard
Rules for Separate Network and Data Links
Chapter 2 65
Fibre Channel hubs are only supported for distances up to 10
kilometers. For distances longer than 10 kilometers, Fibre Channel
switches are required. Fibre Channel switches are always the
preferred solution, since they offer much better performance than
Fibre Channel hubs, which only support Fibre Channel Arbitrated
loop mode.
Refer to the HP 9000 Servers Configuration Guide (available through
your HP representative) for a list of supported FibreChannel
hardware.