What I do to find out which is which is use lsscsi:

    $ lsscsi
    [0:0:0:0]    disk    ATA      ST2000DX001-1NS1 CC41  /dev/sda 
    [3:0:0:0]    cd/dvd  ASUS     SH-224FB         1.00  /dev/sr0 
    [4:0:0:0]    disk    Generic- Multiple Reader  1.11  /dev/sdb