Over the past 15 to 20 years moving head magnetic disks have been the primary device used on computer systems for mass storage. During this time magnetic disks have increased in performance and storage capacity while experiencing a significant drop in cost.
Ronald L. Benton,
"Storage Technology For The 1980s", Proc. SPIE 0318, 1st Intl Conf and Workshop on Picture Archiving and Communication Systems, (14 January 1982); doi: 10.1117/12.967624; https://doi.org/10.1117/12.967624