The areal density of HDDs has not changed substantially
The capacity of mechanical hard drives has increased from 10TB in 2016 to 20TB in 2021, doubling in five years. Although the capacity has doubled on the surface, in fact, the areal density of the disc media has not increased correspondingly and even stagnated for a period of time.
Recently, a report from StorageNewsletter pointed out that the areal density of disc media is hovering around 1.1 Gb/in2, and hard disk manufacturers no longer advertise this indicator in their specifications. Although the areal density of disc media is still increasing overall, it is much slower than in the past. Occasionally, hard drive makers advertise record areal density figures, but more often in the lab than in commercial products.
In the latest 20TB capacity hard drives launched in 2021, Seagate 2021 Exos X20 20TB drive has an areal density of 1,146Gb/in², and WD 2021 Ultrastar DC HC560 20TB drive has an areal density of 1,131 Gb/in². If you move the time forward a little, back in 2017, Seagate’s Baracuda ST5100 had an areal density of 1307Gb/in2. In fact, in 2015, the areal density of Toshiba’s MQ03ABB300 was 1116Gb/in2. The below data shows that since 2015, the areal density of HDDs has not changed substantially.
Seagate has stated that it will develop the second-generation HAMR technology to increase the areal density to about 2.6Tb/in2, and plans to further increase it to 6Tb/in2 in 2030 to support a 3.5-inch hard drive with a capacity of 100TB, but no substantial breakthrough has been seen for the time being. New technologies require completely new read/write heads, disc media, and extensive changes in internal design. Products are unlikely to change so much in a short period of time, so at this stage a conservative approach is being taken when adding capacity, allowing for an incremental and less risky development path. If mechanical hard drives want to grow rapidly again in capacity and areal density, EAMR technology may be needed.
