The sound a hard disk drive makes when you first turn your computer or external storage device on is well-known, with the motor starting to spin, closely followed by a few clicking sounds. If all is fine with the drive, it will quickly settle down with the platters continuing to spin, waiting for the drive to be accessed.
Any change in these sounds, such a different pitch to the spinning or extra clicks from the read/write head should be taken as warnings that the drive may not be completely healthy. If the drive is heard to spin down or it makes a lot of clicking sounds without the computer being able to boot up, the computer should be turned off and the drive sent for data recovery.
The Disk Drive Boot Sequence
When power is applied to a hard disk drive, it checks the status of each chip contained on the controller board, in order to ensure all the electronics are functioning correctly. The drive then performs a self-check of its other components.
If the controller board chips check and the self-test of the other components passes, the drive spindle motor is started, which spins the platters causing debris to be removed from the surface. The spinning platters causes movement of the air or gas contained with the drive to flow, which creates the air bearing, essential for keeping the read/write heads flying at the required height. This airflow causes the guard protecting the read/write heads, which are parked when the drive is powered off, is moved once the air is moving fast enough to ensure they will not come into contact with the platters. When the drive is powered off, the spinning of the platters is used to ensure the read/write heads are moved back to the parking position.
The read/write heads check the servo timings which allows them to located the exact position of the system area and other sections of the drive. The system area is then read from the drive platters, which can include additional firmware and overlays, which is most often stored at the other edge of the platters.
Problems During the Boot Sequence
If the drive servo timings, the system area or the read/write heads are damaged it will result in repeated clicking noises as an attempt is made to access the data. It is also possible that if a hard disk drive is powered up and powered of several times in a very short period of time, that the read/write heads can fail to move back to their parking position, instead becoming stuck to the surface of the platters, which will most likely damage the read/write heads as well as the magnetic recording layer.
Corruption of the firmware or system area information can result in a failure of the drive to boot up. These may result in the drive clicking repeatedly or the platters may spin down. In either case, the drive will probably not be detected by the computer BIOS.
Disk Boot Failure and Data Recovery
If your hard disk drive fails to start correctly and makes repeated clicking noises, or the platters can be head to spin down, you will require professional data recovery. The drive will require the use of donor parts to overcome the issues before a sector-by-sector image of the drive can be secured.
In either situation is important that the drive is powered off as continually attempting to boot the drive up can result in further damage occurring, which could ultimately result in your data files being lost.