On two Supermicro 847E16-RJBOD1 enclosures, I have trouble accessing SATA disks on the rear backplane with 6gb/s. The only significant difference between rear and front backplanes is total cable length from HBA to backplane, which is about 1m + 30cm vs. 1m + 70cm.
SAS signalling shouldn't be affected at these lengths, and I always assumed HBA and backplane will connect with SAS signalling whatever disk type attached. Is this assumption wrong? Do SATA disks limit HBA to backplane cable lengths?