There are many different ways in which Hard Disk Failure can occur; however it could be split into 4 main categories:
1. Electronic Failure
2. Mechanical Failure
3. Firmware Corruption
4. Logical Corruption
It is also possible for the faults to happen in combination with each other, depending on what exactly has happened will determine whether the data is recoverable or not. It is worth noting that over time all hard drives will develop bad sectors, unfortunately this is not preventable and will case data loss.
This fault relates to errors on the controller board, often caused by electrical surges or power spikes, you will recognise this fault as the HD will not spin when powered up and will not be detected. This type of error is not critical in terms of data loss and a data recovery company will be able to recover lost information.
This type of fault relates to the components in the hard drive failing, this will cause data to become inaccessible. This fault can be detected by powering the system up, the hard drive will make a constant clicking noise, indicating a mechanical fault. In order to fix this fault a specialist company must do it as it requires the faulty parts to be replaced from parts on a working drive, this was all the data can be saved.
This error is an embedded software code that when it goes wrong it does not allow the hard drive to interact properly with the rest of the system
These errors are different from the rest as the drive remains fine physically; the errors could be due to a seriously fragmented disk.