From PC World: Some might think the hard disk drive (HDD), which is rarely found in consumer computing devices these days, is obsolete. In truth, it’s nowhere near kaput. Why? Hard drives provide capacity that SSDs can only dream of. At least at anything close to an affordable price.
With the data created each year now measured in zettabytes (trillions of gigabytes), we obviously need all the room we can get. To meet that demand, WD (newly divested of solid state experts Sandisk) plans to squeeze every last drop out of the spinning platter technology using multiple techniques. Including:
SMR (Shingled Magnetic Recording), aka overlapping data tracks. This can slow write performance in some circumstances, but increases capacity.
eAMR (Energy-Assisted Magnetic Recording), or applying more energy to the write head for more precise alignment, and closer packing of bits (tiny, variable-orientation magnetic particles). Again, increased capacity.
HAMR (Heat-Assisted Magnetic Recording), or applying a bit of heat to the surface of the disks making them more responsive to magnetic pulses, also allowing tighter packing of bits.
ePMR (Energy-Assisted Perpendicular Magnetic Recording) — the same as above, but with the bits standing on their toes, i.e., perpendicular to the plane of the disk/platter. Actually, PMR has been the norm for quite a while, and responsible for the huge jump in HDD capacity over the last couple of decades.
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