I am a bit confused by the output of smartctl and the messages log.
sudo smartctl -a /dev/sdd states the following link speed for my hard drive:
ATA Version is: ATA8-ACS T13/1699-D revision 4
SATA Version is: SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s)
while the messages log for the same drive says
ata4.01: ATA-8: ST3000VX000-1CU166, CV23, max UDMA/133