First, and foremost, how did Seagate increase the volume of their drives so radically? To answer that question we must first understand areal density. To paraphrase Webopedia's definition: Areal Density also called bit density is the amount of data that can be packed onto a storage medium. Areal densities are generally measured in gigabits per square inch. The term is useful for comparing different types of media, such as magnetic disks and optical disks. Current magnetic and optical disks have areal densities of several gigabits per square inch.



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