May 03

Inside your laptop hard drive – Whats there?

Many people assume that the inside of a hard drive is extremely complicated and while what it does is complex the inside of a hard drive is not a complicated as you may think. Some may even be surprised at what the hard drive platter looks like (where all that valuable data is stored)

I am often asked what the hard drive is and I often tell people it’s like an old record player as that is the easiest way to describe it with discs and a needle. The gallery below is a laptop hard drive that has failed that I have taken apart to photograph.

Laptop hard drive front and back after removal from laptop

The original drive in its normal state straight out of a laptop. The PCB on the reverse is a controller board and it is it what interacts with your Laptop and controls the motors and heads.

laptop hard drive frontlaptop hard drive back







Drive back board removed and Drive back

The hard drive with the PCB removed.

laptop hard drive main boardhard drive bottom no board








Hard drive top lid removed

After the top of the hard drive is removed you can clearly see that the actually inside of the drive does not contain very much. It contains the platter (the shiny disc) and the arm that controls the read write headers and a small circuit board. Holding the arm are very strong magnets which can be seen in picture 1 (they are removed on picture 2) these are used to position the head.

hard drive lid removedlaptop hard drive inside






Hard drive read write headers

You can see the read write heads in the 2 pictures below these are the bits that read that data from the spinning platter. The arm you can see holds the read write heads and is very fast and very light meaning it can move from one side of the platter to another very quickly

read write headsread write heads 2








Hard drive platter


The hard drive platter is where all your data is stored and are basically 2 discs usually made from aluminium, glass, or ceramic that are coated in a magnetic material as well as protective coatings.

On this picture and the one above you can see the 2 platters of the hard drive. These spin on a motor in the case at a rate of 5400 RPM but on some faster driver can spin up to 10000RPM.

Some drive have more than 1 platter it depends on the capacity of the drive.


Magnets and PCB Socket

magnets from hard drivesPCB connector

The socket (right picture) connects the arm to the PCB

The first picture is the magnets that site on either side of the arm. These are very powerful magnets and I use them to magnetise my screwdrivers!

The most widely used type in hard drive is a Neodymium magnet which is a rare earth element. The following quote was taken from a site called 7 volts that unfortunately no longer exists but gives a good explanation of magnets in a hard drive

The magnets are used in the mechanism that positions the heads. The magnets provide a strong magnetic field.  Within the magnetic field is a coil. In order to position the heads, a current is passed through the coil generating a magnetic field within the coil.  The interaction of this magnetic field with the permanent magnetic field  generates the force that moves the heads. By varying the current in the coil, the heads can be precisely placed on the disc. In order to move the head mechanism very quickly from track to track, a very powerful magnetic field is required. If the magnetic field is weaker, there’s less force moving the heads and the drive access time will be slower. Since drive manufacturers strive for the fastest access times, they must use the most powerful magnets they can find. Drive manufacturers have made great strides in making the read write heads and mechanisms much smaller and lighter. This means the later drives need much smaller magnets but they still need to be very strong or access times will suffer. The scientific reader will probably wonder why electromagnets aren’t used instead of permanent magnets for the magnetic field. The answer is probably that heat production and power consumption would be dramatically higher with electromagnet use. Still, it was a good thought and I’m glad you thought of it.

These magnets are a little different from what would be expected.  They’re actually polarized with the poles on the flat surfaces of the magnets rather than at the ends.  Most magnets will be “N” at one end and “S” at the other.  These will have “N” on one flat surface and “S” on the other.