A common misconception about hard drive data recovery is that repairing hard drives means replacing parts. If only it were that easy! Hard drive technology is always changing— manufacturers are constantly using different mechanical designs.
The mechanical precision of today’s hard drives makes head assembly replacement nearly impossible without specialized tools. Platter removal is dangerous and will affect how the drive reads the sectors. As previously mentioned if just one component is out of alignment, the drive will not find the required sectors. If the hard disk electronics cannot find the sectors requested by the controller, it may endlessly try to find those sectors or it will shut down the unit.
Mechanical precision is just one side of hard drive technology – the electronics are just as finite. Exchanging circuit boards between drives used to be a quick way to work around a failed circuit board in the past. The electronics are much more complicated, and as a result the different revisions of a circuit board are rarely compatible. The innovations of the past 15 years have made a circuit board swap as a solution a thing of the past.
Today’s hard drives have no room for errors when it comes to platter and head alignment. The tolerances are so exacting that hard drive manufacturers even design ways to keep the Base-Casting Assembly, where all the components are attached to, from shifting due to high temperature situations. For instance, one hard drive manufacturer of high performance SCSI based drives actually designs their Base-Casting Assembly with pre-stress points. The assembly does not line up from corner to diagonal corner—it’s pre-torqued. When the casting assembly heats up, the unit actually twists back (thermal expansion) into a true line-up from corner to corner. With the byte-density of most large hard drives today being 4gb to 6gb per square inch, absolute precision is required for these high capacity and high speed drives to operate reliably. Hard disk manufacturers are working to increase how many bytes can be squeezed into a square inch.
Today’s hard drives are designed from basic primary components as the foundation first and then other components are built around that. For instance, research and development improvements in platter and magnetic media require research and development improvements in head design. These designs require that the electronics be ‘custom-made’ for that drive. Hard drives are ‘fine-tuned’ to the properties of the storage media and read/write heads. Similar to how a radio is tuned to a specific radio frequency; hard drives are finely tuned to complement data signals that are read from the storage media.
Hard drive manufacturers make large batches of drives so there will be similarities between drive models. However, the Revision Code (proprietary hard drive read-only software that is used by the electronics to manage and operate the hard drive) changes frequently within the same model and batch. Hard drive innovation requires drives to be constantly improved upon. All of this requires extensive training in electronics and computer science to be able to work with these storage devices.