A sealed head disk assembly has a cover for enclosing major components of
the head disk assembly. The cover has a hermetic seal encompassing an
outer perimeter of the cover and a semi-hermetic seal inside a perimeter
of the hermetic seal. The hermetic seal and semi-hermetic seal are
juxtaposed to at least one complementary surface on the base casting. The
base casting, which provides attachment points for the major components
of the head disk assembly has at least one complementary surface.