In its early years, the disk drive industry was led by a group of large-scale, integrated firms of the sort that Alfred D. Chandler, Jr., observed in his studies of several of the world's largest industries. The purpose of this history is to explore why it was so difficult for the leading disk drive manufacturers to replicate their success when technology and the structure of markets changed. The most successful firms aggressively developed the new component technologies required to address their leading customers’ needs, but this attention caused leading drive makers to ignore a sequence of emerging market segments, where innovative disk drive technologies were deployed by new entrants. As the performance of these new-architecture products improved at a rapid pace, the new firms were eventually able to conquer established markets as well. As a consequence, most of the integrated firms that established the disk drive industry were driven from it, displaced by networks of tightly focused, less integrated independent companies.