We Need A Boost In HDD Areal Density!

The 2022 IEEE TMRC meeting gave interesting insights into the future of magnetic recording, particularly hard disk drive (HDD) recording. In this article I will look at past and future roadmaps for HDD technology and compare those roadmaps for actual shipping product areal densities (how many bits you can store per area on a disk). We will also look at other ways to increase HDD capacities, besides increasing the areal density.

The Advanced Storage Research Consortium (ASRC) released an updated HDD areal density roadmap which was on display at the TMRC, shown to the right below.

To the left is a similar roadmap from 2014 by the then Advanced Storage Technology Consortium (ASTC). Note that the 2014 roadmap projected a 30% cumulative annual growth rate (CAGR) for HDD areal density starting in 2017. The more recent roadmap shows about a 22% CAGR if we follow the HAMR (heat assisted magnetic recording) path.

I have been tracking HDD product and laboratory areal density demonstrations for several years and the chart below shows actual announced shipping product areal densities (see the figure below).

We note that there was a spurt of growth in HDD areal density in 2015 and 2016, but, except for small bump in AD in 2021, there has been little growth in HDD announced shipping products since 2016 (6 years in 2022). We hope that the new roadmap will be successful since increasing the digital information storage capacity on individual disks is the most cost-effective way to increase the storage capacity of HDDs.

Another way to increase the storage capacity of HDDs is by adding more disks and heads and this approach is a key element in achieving higher storage capacities for HDDs over the last few years. In particular, Western Digital’s 22 TB HDD announced this year uses 10 disks.

Hoya (a manufacturer of glass HDD substrates) had an exhibit at the TMRC showing a path towards increasing the number of disks in a conventional 3.5-inch HDD enclosure. These included displaying a HDD with 14 disks and an head actuator and one with 24 disks, but no actuator. These are shown below. 24 disks is pretty impressive—very thin disks, but there is little room to include an actuator to move the heads over the disks.

The ASRC poster also showed some projected requirements to achieve 2 and 4 Tbpsi recording densities as shown in the image below.

These projections are with HAMR, which appears to be the path to increase HDD areal density. MAMR and other energy assisted magnetic recording technologies are seen as short-term improvements. The talks at the TMRC seemed to be focused mostly on achieving 2 to 4 Tbpsi. This is very different than say 8 years ago when 10 Tbpsi drives that could enable 100TB 3.5-inch HDDs were envisioned by 2025. It has become much harder to increase HDD storage capacities. Seagate has said that they intend to introduce a HDD with 30+ TB by 2023. It would be great if this was with higher areal density and not just more HDD components.

The 2022 TMRC gave some insights into the development of HDD technology. For about 6 years HDD areal density hasn’t increased much above 1 Tbpsi. The current ASRC roadmap projects about a 22% CAGR in areal density out to 2034. We hope that higher disk capacities will be achieved in the next generation of HDDs.