Introduction to Hard Disk Data Recovery
If you want to know what Data recovery is, you should learn the physical structure of the hard disk and how the data is stored on a drive.Typically hard disk is a sealed unit of one or more circular platters mounted on a common spindle. Electromagnetic read/write heads are located just above and below each platter with a clearance of as little as 3 Nanometers. The platters rotate at a constant speed, eg: 5400rpm, 7200rpm & latest enterprise-grade disks are rotating at a speed of 15000RPM.
Platters are circular disk made of a non-magnetic material typically aluminum alloy, glass or ceramic and are coated with a thin layer (10-20nm) of a magnetic material.
Read/write heads are typically made of extremely small horizontal magnetic blades, are designed down to the nanoscale and attached to an actuator arm. By changing the electrical polarity of bits on a magnetic disk, the read/write head effectively store/retrieve data on magnetic platters in the form of 0’s and 1’s.
Spindle motor plays an important role in hard drive operation by turning the hard disk platters. Many hard drive failures occur due to spindle motor not functioning properly.
Hard disk logic PCB is made with an intelligent circuit board integrated into the hard disk unit. It is mounted on the bottom of the base casting exposed to the outer side. The read/write heads are linked to the logic board through a flexible ribbon cable.Now we will speak about Hard disk failures and data recovery. Main reasons for a drive failures are
- Electrical Failure – if the PCB gets damaged due to power surges or power spikes, you lose access to your data.
- Mechanical Failure – Mechanical damage normally arises as a result of impact, Fire or water damage. Internal components like the read-write head and motors, can become faulty without prior warning.
- Logical Failure – It refers to any other non-physical failure types. It can be the easiest or the most difficult recovery job depending on the circumstances that leads to logical failure.
- Firmware failure – Firmware is the software program normally only accessible by the disk manufacturers. It is used to do low level disk testing and functions that are directly responsible for the proper functions and healthy state of hard disk. Modern disks normally have their firmware codes located on data platters and also the PCB board. 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.
- Bad platter surface – This is commonly called as bad sectors which are not accessible for reading or writing operation. The main cause is due to damages on platter surface, head crash, manufacturing defects and tracking errors.
Head replacement recovery is the most complex case. It requires cleanroom facility and a high level of technical competency. Laboratory for head replacement requires space which is 100 times cleaner than a Hospital operating room.
We have received many cases where customers opened up their hard disk as initial troubleshooting method and made the drive unrecoverable. Simple fundamental of this is if you allow a small dust particle inside the disk chamber and turn on the drive, the platter surface will become a sand paper.
See the below video of Seagate Hard Disk manufacturing process.