Magnetoresistive (MR) head technology is used in disk drives to allow higher storage densities than the older inductive-head technology. MR heads provide up to four times the storage densities possible with thin-film inductive heads. Almost all of the major storage vendors now sell drives based on this technology, which started to become popular in the late 1990s.
MR heads have separate read/write elements - with each optimized for its particular function. With inductive-head drives, one head performs both tasks, leading to some performance problems as it tries to read and write data simultaneously. MR drives also have less noise, meaning fewer corrective reads or writes.