Hard drives have two extremely powerful neodymium magnets in them anyway, attached to the arm which moves back and forth. Millimetres from your platters. I have

Hard drives have two extremely powerful neodymium magnets in them anyway, attached to the arm which moves back and forth. Millimetres from your platters. I have a hunch that a fairly steady magnetic field is probably fine, it's erratic/alternating magnetic fields which are likely to kill things.