Users are complaining the response times are out of range on a retail application. Performance monitoring of the storage subsystem indicates that there are no problems. A check of the host error logs

Using 9 micron fiber typically refers to single-mode fiber, which supports much longer distances than multimode fiber and would generally improve, not worsen, signal quality over long distances, making it an unlikely cause of re-transmit errors.

While a small SCSI timeout value could cause timeouts, the question specifically points to excessive SCSI re-transmit errors and a recent HBA upgrade, suggesting a physical link issue rather than a software configuration one as the most probable cause.

If the switch port were set at 2Gb/s while the HBA is 4Gb/s, they would typically negotiate down to 2Gb/s, resulting in lower performance but not necessarily excessive re-transmit errors or timeouts unless the HBA was hard-set to 4Gb/s without auto-negotiation, which is less common and less probable than a distance issue given the context.

While 4Gb/s HBAs and switches can support longer distances with appropriate fiber, common multimode fiber optic cables (like OM1 or OM2) have distance limitations that decrease as speeds increase. Exceeding common 4Gb/s limits for specific multimode fibers, such as approximately 175 meters, can cause signal degradation, leading to excessive SCSI re-transmits and timeouts due to lost or corrupted frames.