One question: why are you using hdparm on the partition device (sdb1) and not on the disk device (sdb)? I'm not sure it's the same. In any case, with hdparm -i /dev/sdb can you see whether the UDMA is being used?
One question: why are you using hdparm on the partition device (sdb1) and not on the disk device (sdb)?
I'm not sure it's the same.
In any case, with hdparm -i /dev/sdb can you see whether the UDMA is being used?