What is the capacity of a single-sided dual-layer DVD disc?

[SanPaige]

The capacity of a single-sided dual-layer DVD disc can reach 8.5GB. A DVD disc consists of two substrates, with each substrate capable of holding up to two layers of data. A disc (disk) is the medium that carries data storage in a hard drive. Hard drive discs are made of durable materials as the base, with magnetic powder attached to the surface of an aluminum alloy (new materials may also use glass) disc, which is processed to be very smooth. These magnetic powders are divided into several concentric circles called tracks, and on each concentric track, there are countless randomly arranged tiny magnets representing the states of 0 and 1. When these tiny magnets are influenced by the magnetic force from the head, their alignment direction changes accordingly. By using the magnetic force of the head to control the direction of specific tiny magnets, each tiny magnet can be used to store information. A hard drive is composed of multiple discs stacked together, separated by spacers. Most modern disk discs use thin-film composite technology. The structure of a hard drive's medium film is roughly as follows: lubrication layer, carbon coating, magnetic layer, buffer layer or underlayer, and substrate.