6.3.14 Hard Disk Drives (HDD) Introduction  Hard Disk Drives (HDDs) have served as the primary memory and data storage in computers since IBM introduced the model 3340 disk drive in 1973. Nicknamed “the Winchester”, because it had 30MB of fixed memory and 30MB of removable and the working designation of 30/30 resembled, in name at least, the famous rifle, it pioneered head designs that made operation of the hard disk viable. Subsequent reduction in size and more recent developments in head and disk design have greatly increased the reliability of disk drives, leading to the robust designs in common use today.  Data managers whose responsibility it is to maintain data have considered the hard disk too unreliable to use as the sole copy of an item, and too expensive to use in multiple, and consequently more reliable, disk arrays. The data on HDDs has consequently been duplicated on multiple tape copies to ensure its survival. As stated above (6.1.4 Practical Aspects of Data Protection Strategies and 7.6 Archival Storage) all data systems must have multiple and separate copies of all data. While experts tend to agree that the most reliable data system consists of a HDD array supported by multiple duplicates on tape, the continued reduction in costs and improvement in reliability make the concept of identical duplicates of data on separate hard disks a possibility. The principle of multiple media remains, however, and disk only storage constitutes a risk.