Has HDD Areal Density Stalled?

This article was recently written by Tom Gardner, treasurer and webmaster at IEEE Silicon Valley History Committee.

 
HDD companies used to brag about achieving a new highest areal density benchmark but all have gone silent and apparently Toshiba does not publish such data.

Areal density seems to occasionally be published in some data sheets but if you can find OEM manuals it is more often published therein. 

In the interest of full disclosure, the following is based only on the latest highest capacity drive material posted at the 3 HDD manufacturer’s sites and may have missed other product data and Toshiba’s data may be available to selected customers.
 
The following are current highest areal densities for the latest 20TB HDDs:

• Seagate 2021 Exos X20 20TB drive at 1,146Gb/in² average
• WD 2021 Ultrastar DC HC560 20TB drive at 1,131 Gb/in² maximum

Seagate admits to having 10 disks, WD is silent.

HDD Shipping Product Areal Density Growth

 
Note the scare quotes added around “average” areal density of the Seagate drive. What does that mean? The industry used to publish the maximum areal density calculated as the tracks per inch times bit per inch at the most dense zone resulting in a “maximum” areal density as WD labels it. 

But today the zone sizes and areal densities within each zone are optimized during production so the highest areal density on any given drive is not likely highest actually achieved in the most optimized drive allowed by a production process. Perhaps average is some average of the maximums over a statistically significant lot of production or simulated drives – who knows?
 
Be that as it may, according to published data the industry reached 1,116Gb/in2 in 2015 with the Toshiba 3TB 2.5-inch MQ03ABB300 and in 2017 achieved 1,307Gb/in2 with the Seagate Baracuda ST5100.
 
This suggests that regardless of all the talk of EAMR, the HDD industry has not made any substantive improvements in areal density since 2015! That goes a long way to explaining the silence.
 
Food for thought?

Editor’s note: Areal density are now only increasing for 3.5-inch nearline HDDs. No new 2.5-inch units have been released since 2018 in a market decreasing due to competition of SSDs.