 The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory (then typically drums) but faster and more expensive than tape drives.The commercial usage of hard disk drives (HDD) began in 1957, with the shipment of a production IBM 305 RAMAC system including IBM Model 350 disk storage.US Patent 3,503,060 issued March 24, 1970, and arising from the IBM RAMAC program is generally considered to be the fundamental patent for disk drives.