To understand how perpendicular recording has changed hard disk storage and increased storage capacities, you first need to understand conventional, longitudinal recording.
Longitudinal Recording
As indicated by the name, longitudinal recording is a method of recording data to a hard disk drive (HDD) in such a way that (de telle sorte que) the data bits are aligned horizontally in relation to the drive's spinning platter, which is parallel to the surface of the disk. Essentially, you are recording on a magnetic material, where bits (a collection of magnetized particles) are laid out end-to-end (de bout en bout
). Longitudinal recording is the actual (reelles) method of how the bits are recorded on disk platters. The direction of this magnetic charge is horizontal to the media, meaning the north and south poles of the magnetized particles are lined parallel to the surface of the disk.
Longitudinal recording has been the standard method (méthode standard
) of recording for more than 50 years — the first commercial hard drive was introduced in 1956. Over the years we have seen many technological changes to longitudinal recording, which have resulted in higher-capacity drives. We've moved from 5.25 inch drives to 2.5 inch drives; the number of platters and heads have been reduced all the while increasing areal density (which is the amount of data per square inch of media). With all of these changes however, the need to physically change the way data was written to the drive, was also being considered to reach (pour atteindre) higher storage capacities. Vos notes pour comprendre

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Image Source: Hitachi Global Storage Technologies - Perpendicular Recording

Storage capacity with longitudinal recording was largely increased by decreasing the size of the magnetic grains that