After a whole week battling with this issue on my own, I am now exhausted and seek your professional opinions.
I have a GA-F2A88XM-DS2 mobo with integrated AMD RAID controller.
I have 3 HDDs:
250 Gb WD2500AAKX-001 CA0 (bought some time 2012, OS installed on it)
3 Tb ST3000DM001-1CH166 (bought April 2014)
3 Tb ST3000DM001-1ER166 (bought January 2015)
and an external 2 Tb ST2000DM001-1CH164 which I use for backup.
Now, if BIOS is set to AHCI or IDE,...