hdd failure

Electrical Failure
PCB gets damaged due to power surges or power spikes, you lose access to your data.
•Drive is powered, but shows no sign of function
•Disk knocking as the motor fails to spin
•Clicking sound as the heads search or initialize

Mechanical Failure
Mechanical damage normally arises as a result of impact or wear and tear.
On most occasions when there is a failure of the read-write heads the hard disk will spin up and then make a repetitive clicking sound. This is sometimes known as the ‘click of death‘. To recover the data when there is a failure of the read-write heads it is necessary to replace the head assembly of the failed hard disk drive with that of a working donor. Head stuck to the platter - Mostly found in laptop drives because of the motion sensor. If a hard drive senses it falls it will stop the platter. If the platter stops faster than the head can park, the head will lose altitude, touch the platter and get stuck.
Head crashes can be caused by electronic failure, a sudden power failure, physical shock, contamination of the drive’s internal enclosure, wear and tear, corrosion, or poorly manufactured platters and heads. HDDs require a certain range of air pressure in order to operate properly. The connection to the external environment and pressure occurs through a small hole in the enclosure (about 0.5 mm in breadth), usually with a filter on the inside (the breather filter). If the air pressure is too low, then there is not enough lift for the flying head, so the head gets too close to the disk, and there is a risk of head crashes and data loss.

Firmware Failure
 If the firmware area of the platter is corrupted, the drive will appear to have failed even all the electrical and mechanical components are still fully functional.
•drive powers up, but is not recognised by the computer
•drive powers up, but is recognised wrongly, sometimes with nonsensical characters
•drive freezes during booting up