From what I understand,
hdx is naming convention for IDE (PATA) drive,
sdx is for SCSI (SATA) drive.
Sometimes I see sd0 and sda, similary hd0/hda. What are their differences ? When would we use number in naming such as sd0 or hd0 ?
It seems that (hd0, x) is only used by GRUB, is that correct ?