There will be a big increase in areal density, these disks will use platters with about 1.5Tbpsi (Terra-bit per square inch) areal density, about 50 percent higher than today, but total storage capacity will be only 4TB.
Seagate's HAMR technology involves heating the part of the magnetic platter that is being written to. By applying a temperature of around 450°C using a laser with a 810nm wavelength and 20mW power, the magnetic properties of the disk change for a short time, allowing writing on a much smaller scale.
The reason why the first disks offer a storage capacity of only 4TB is because current lasers are thicker than traditional write heads, this means the distance between the platters increases compared to today's HDDs and reduces the number of platters a disk can house.
These test models are supposed to demonstrate whether HAMR is ready for mass production, the current schedule is for mass production to commence sometime in 2018.
HAMR is only the first step in a series of advanced recording technology for HDDs. Advanced Storage Technology Consortium (ASTC), which unites numerous makers of hard disk drives as well as developers of storage solutions, last year showcased a roadmap of HDD evolution. The roadmap covers multiple magnetic recording technologies and spans to 2025 and beyond. ASTC expects hard drives with 100TB+ capacities to emerge around 10 years from now.Via: KitGuru