Types of hard drive failures
Considering the technological complexities concerning hard drive design and operation, it is no surprise that failures do occur. Hard drive failures can present themselves in any number of ways, determined by the cause of the failure.
This implies that the physical components of the hard drive are functioning correctly, however there is damage to the logical (software) part of the drive. The hard drive can be seen by the computer, but the user cannot find or access their data. The most common cause for this type of failure is incorrect user action or virus attack. The user can accidentally delete a file or format a partition, or a virus may infect the computer causing damage to file structure making access to the files impossible. The longer the period of time the computer is used after this type of failure the lower the chances of recovery become.
Failure of the hard drive’s printed circuit board (PCB) can result in the hard drive not powering up at all. Sometimes burnt components can be seen or smelt on the PCB. Data recovery for this type of failure includes repairing or replacing the PCB. Special ‘adaptive’ information is stored on each PCB unique to the hard drive it is attached to. This information needs to be transferred to a perfectly matched replacement PCB, requiring expensive and specialist equipment for some brands of hard drive.
Bad sectors develop on the hard drive’s magnetic platters over time. They can present themselves in many ways, such as struggling to access certain files on the computer. In more extreme cases it can cause the computer to freeze and not function, or even revoke all access to user data. Drives in this state need to be cloned using expensive and specialist equipment, following which the clone is analysed and the data extracted and recovered.
Firmware is the code stored on the hard drive itself that basically provides the environment for the hard drive operate in. Sometimes these service area modules become damaged or corrupt which will result in the hard drive not being accessible. Firmware performs a highly complex function and requires expensive and specialised equipment to work with. The smallest mistake in firmware modification can result in total data loss and zero chance for recovery.
A drive with a physical failure will often fail to be seen by the computer and often make a clicking sound, or no sound at all. The read/write head assembly inside a hard drive is made up of heads that ‘fly’ nanometers above the hard disk surface as they read and write data. These can fail for a number of reasons, from static to physical damage to old age. The replacement of these heads requires opening of the hard drive in a perfectly dust free lab environment and swapping out the required parts. This is an extremely complex task and part matching is a complicated procedure. To find the perfect part it is sometimes required to source it internationally. These read/write heads can sometimes get stuck to the platters resulting in ‘stiction’. Hard drive motors can also become jammed in which case the drive will not spin up at all.
Below are some images and further descriptions of common hard drive failures:
This occurs when the read/write head assembly makes contact with the disk platter/s. This can be caused by a failure of the internal components or by a physical force, such as the hard drive being dropped. Contamination within the hard drive enclosure (dust or any other particles) is also a cause for a head crash. Below is an example of such a failure, where the head slider has come right off the head assembly and resulted in multiple scratches on the disk surface.
The printed circuit board (PCB) houses the electronics of the HDD. A power surge or ‘dirty’ power, overheating or general wear and tear can cause damage to the PCB. Sometimes this damage is restricted to the PCB itself, othertimes it finds its way into the HDD internals as well, such as the preamp on the head assembly. This would require both PCB and head assembly repairs/replacement. Below is a PCB with a burnt motor controller chip, caused by a poor quality power supply.
Weak heads and bad media
If the read/write heads become weak they are unable to read data from the drive. This can also occur if the magnetic surface media deteriorates. These circumstances will result in certain sectors on the HDD being unable to be read. Below is an example where multiple sectors are failing to read (black blocks).
Common failures and symptoms
— Hard drive is visible but not accessible from within Windows (or other operating system) or seems to contain no data.
> An accidental format or virus attack could destroy file systems or partition tables.
= Hard drive data recovery in this instance could involve having to repair the file system.
— Hard drive does not spin up at all.
> This could be caused by faulty electronics (PCB) or a seized motor spindle.
= Hard drive data recovery in this instance could involve PCB repair or replacement, or working around the seized spindle issue.
— Hard drive spins up as per normal, but is not detected in the BIOS of the computer.
> Corrupt firmware or ROM, faulty electronics (PCB) or read/write head failure could be the cause.
= Hard drive data recovery in this instance could involve PCB repair or replacement, firmware repair or head assembly replacement.
— HDD spins up, numerous clicking noises are heard, the drive might spin down again.
> Corrupt firmware or ROM, read/write head failure are amongst some of the causes.
= Hard drive data recovery in this instance could involve PCB repair or replacement, or head assembly replacement.
— Hard drive spins up, grinding/screeching noises are heard, the drive might spin down again.
> This is known as a head crash, when the read/write head assembly comes into contact with the magnetic layer. This is a bad scenario as the head assembly scrapes off the magnetic layer as the drive spins, losing that data forever.
= Hard drive data recovery in this instance could involve head assembly replacement and other techniques for hard drive repair.
This is merely a small list of possible combinations of symptoms and likely causes relating to hard drive failures. Every instance is different and presents itself as a unique problem.