A hard disk drive system (10) includes a rotating magnetic disk (16), and a support arm (22) which is supported for movement relative to the disk under control of a voice coil motor (21). a microactuator (26) supports a read/write head (27) on the support arm for movement relative thereto a control arrangement (13) controls the voice coil motor and the microactuator in response to position information (31), which is read by the read/write head from the disk and which indicates the position of the read/write head relative to the disk. The system is free of a sensor for detecting the actual position of the support arm relative to the read/write head or the disk.