FIRST, YOU NEED TO UNDERSTAND A FEW VERY IMPORTANT THINGS ABOUT HARD DRIVES:
First of all let’s start by drawing a picture so that you can visually see what were discussing here.
Inside a hard drive there are moving components, it’s sort of like a record player.
This is one of the easiest ways to describe what it looks like inside the actual case of a hard drive when dealing with a professional data recovery company.
The just like a record player there are discs called platters. Platters are where the data is written to and read from.
Similarly, the read/write heads are components of a hard drive located at the end of the actuator arm, and they are responsible for reading and writing the data to the platters.
When the needle on the record player is damaged it needs to be changed out in order to properly read the record.
This is the same process an experienced hard drive recovery service will peform during recovery cases when failed read/write heads are preventing progress.
These heads actually float on the air produced from the rotation of the platters as they are traveling anywhere from 5400 to 12000 RPMs, depending on the hard drive and its speed.
Read/write heads on a hard drive can go bad for many reasons:
Inside a hard drive there are usually multiple platters stacked on top of each other. Data is written to the top and the bottom of the platters usually, in which case there will be a read/write head on the top and also on the bottom of each platter.
So in other words if a hard drive has three platters, there’ll usually be six read/write heads.
When there is a read write/head failure on a hard drive that needs repair, that particular head that has failed will not be able to read or write data on the platter.
When this happens the drive may be partially functional with specialized data recovery equipment, or it may not be able to initialize at all.
You may hear:
Just because there is a read/write head failure, doesn’t mean they have all failed. One or more can fail at any time, and the rest may operate just fine.
However when there is a head failure it is likely to cause platter damage and kick up dust that will float throughout the drive and cause the other heads to fail.
It’s absolutely crucial not to power on the drive if it will not initialize or be recognized by a computer. Clicking noises are a sign that there may be a head failure, or a failing head.
Depending upon which head fails, will determine whether any of the data on the drive can be recovered without performing a head swap. If the head that reads the service area is faulty, then the drive will not be able to initialize in any circumstance.
With professional data recovery equipment, trained engineers may be able to image the drive utilizing the good heads, and turning off the bad heads.
This will result in an incomplete image and a partial recovery.
In this case, it will be necessary to replace the whole head stack in order to have a full recovery and complete image of the drive in question. (It is not possible to replace just one head from the stack.)
Changing the read/write head stack assembly is a very tedious process that requires expert skill, experience, and the right environment.
This also requires a suitable donor set.
Imagine a patient with a bad liver that needs a transplant. It’s very similar to the situation as the donor has to match the patient almost exactly depending on the manufacturer of the hard drive.
Once a suitable donor set has been found, a clean room environment is necessary in order to have an atmosphere that is dust free. The industry standard for clean room data recovery is ISO 5 CLASS 100.
The heads from the donor drive are removed, and transplanted into the patient. Any mistake during this process can ruin the donor heads, and potentially scratched the platters.