Write Pre-Compensation

In the hard disk inner sectors the magnetic charges are so close that they can move if they are located near to other charges. For example, if a north charge is too close to a south charge, they will move towards each other, while if a north charge is too close to another north charge, they will move apart. If this happens stored data can be modified – i.e. corrupted, since it will assume a different value from what was originally stored.

The solution for this problem is called write pre-compensation. Data is stored “wrongly” (i.e. in the wrong place) in order to be in the correct place after the natural forces of attraction and repulsion moved the magnetic charges, thus not corrupting the stored data.

In the old days it was necessary to configure the hard disk drive with the track number from which it would start using write pre-compensation. Nowadays this is automatically done and you should not worry about this.