By David John Hughes
Hard Drive Anatomy
In order to explain why removing the cover of a hard drive is not a particularly good idea it is helpful to understand a little about how a hard drive stores, and accesses, your data.
Inside a hard drive is a circular disk on which your data is stored magnetically and is then accessed by a read/write head which hovers above the platter (very close - only a matter of microns) and interprets the magnetic data. These disks rotate at an incredibly high speed (usually 5400rpm or 7200rpm). The circular disk (commonly referred to as the platter) is usually constructed of aluminium or glass but has a very thin special coating over the top where the data is on the platter will be stored.
This special layer is extremely sensitive and due to the speeds at which the patter spins inside a hard drive can easily be damaged by the smallest of particles such as dust and other airborne contaminants. If you think this is an exaggeration then what you have to remember is that at 7200RPM a small piece of dust hitting against a very thin layer that contains your valuable data will be travelling at an incredible speed and this spells trouble for your platters surface.
Why A Class 100 Clean Room is so Important
As highlighted above, if you get any tiny particles of dust inside your hard drive then this will cause big trouble as soon as the drive spins again. In your home or at an office there are typically 500,000 to 1,000,000 airborne particles 0.5 microns in diameter or larger for every cubic foot of air - so as soon as you remove the cover from a drive in this environment you are in big trouble!
A class 100 clean room is a specialised environment in which there is less than 100 airborne particles (<0.5 microns diameter) per cubic foot of air. It is in these environments in which hard drives are built in the first place - they are assembled fully and then sealed so that no dust particles can enter the drives once they are shipped out to retailers.
If there is ever a need to open a hard drive for data recovery (e.g. a swap of read/write heads or a change of spindle motor) then it must be performed in a class 100 clean room by a professional data recovery specialist or you run the risk of permanently damaging your data. There are of course numerous examples of people on the internet that claim to have successfully opened/repaired drives at home but you can bet for every success story there are probably 100 people that have lost their data for good.
The bottom line is never open a hard drive at home unless you cannot afford to pay for a professional data recovery specialist or you do not consider the data valuable enough to risk losing.
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