A low profile disk drive unit includes a disk; a HSA cooperating with the disk; a base plate comprising a bottom portion for supporting the disk and the head stack assembly thereon and a base plate sidewall extending from circumference of the bottom portion; and a top cover comprising a top portion and a top cover sidewall extending from circumference of the top portion and assembled with the base plate; wherein the top cover sidewall is thinner than the base plate sidewall, and the base plate sidewall is lower than the disk with the bottom portion as a reference datum so as to define an airflow channel between a periphery of the disk and the top cover sidewall of the top cover.