The rapid increase in the volume of digital data is driving demand for effective and economical storage media. As a result, HDD (hard disk drive) shipments are currently rising. And nothing is more integral to HDDs than the platters that store all that data.
Hard drive platters consist of an underlying physical substrate covered with a magnetic coating. But this seemingly simple design hides considerable inventiveness. While denser storage is crucial in maintaining HDD’s $/TB advantage over SSD, it can’t be achieved without well-designed platters!
In this article, we will look at what goes into effective platter design, and how major industry players factor approach the task. We will then look at some of the cutting-edge platter innovations that will keep the storage world on its toes in the years ahead.
HDD’s Yo-Yo Moment
Like a yo-yo, the HDD market is bouncing back fast after a several-year slump in demand for HDDs. In the aftershocks of the pandemic, 2023 saw a 37% decline in unit volume shipments of high-cap nearline from 2022. Now, Coughlin Associates estimates that the unit volume shipment of high-cap nearline HDD rose by 42% y-o-y in 2024. Over the same period, the firm estimates that overall HDD shipped capacity increased by 39%, while HDD market revenue increased by 45%.
These figures signal sustained growth in demand for HDD, with shipments expected to rise even more in the near future. Coughlin predicts total HDD capacity shipments will increase from an estimated 1.2 ZB in 2024 to a sizable 7.3 ZB by 2029. A staggering 90% of this capacity will be in high-cap nearline drives, with HDD manufacturers entering into long-term agreements with major customers to meet increased demands and avoid overproduction.
Meeting this demand will require a substantial increase in HDD components — including, of course, platters. Tom Coughlin pointed this out way back in mid-2023. “We project a doubling of head and media demand by 2028,” he explained at the time. His prediction assumed “a recovery in the nearline market starting in later 2023 or early 2024.” Clearly, the prediction was correct, lending credence to the doubling of magnetic media demand which he now foresees.
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With so much data to store, price matters. HDD currently maintains a solid $/TB advantage for flash, which will likely help HDD keep its key role in nearline storage for years to come.
How Platters Work
Hard drives store bits of information on a physical medium. This medium is in the form of one or more spinning platters that are coated with a magnetic material. These platters, also known as disks or plates, represent data via the polarity of magnetized grains on their surface. HDDs have a write head capable of altering the magnetic polarity of these grains, storing data as 0s and 1s.
The setup may look simple, but a lot of careful consideration goes into optimizing platter design.
- Durability: Your disk is no good if it breaks or damages easily from the recurring write-and-read processes.
- Smoothness: This allows the write head to operate within a few nanometers of the disk without touching it.
- Grain density: Dense storage requires magnetic grains to be small and close together. However, they cannot be so tightly packed that they magnetically interfere with each other.
A hard drive platter is comprised of three main layers. There’s the underlying substrate, a magnetized layer above that, and finally a very thin layer of lubricant.
The substrate is typically made of aluminum, glass, or ceramic, with glass increasingly the substrate of choice due to its superior properties. The thin magnetic layer, which contains the actual grains, is often made of cobalt-alloy. Finally, a carbon-based thin protective coating is applied on top of the magnetic layer as lubricant.
Within this basic setup, there’s a lot of variation. Manufacturers experiment greatly with the materials to increase capacity and performance.
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All else being equal, using fewer higher-cap drives is cheaper and more energy efficient than using more low-cap drives. Platter design is just one element of a race to 50TB HDDs.
Major Players
The hard drive industry is dominated by the Big Three: Seagate, Western Digital, and Toshiba. Some companies, such as Seagate, produce most of their components in-house. This gives them better control over production, at the cost of greater exposure to downturns. The other two companies mostly rely on external suppliers to produce their HDD platters.
For its part, Seagate’s long-term investment in heat-assisted magnetic recording (HAMR) technology may now be paying off. The firm plans to ship 32TB HAMR drives in volume in 2025. Its HAMR platters use superlattice platinum-alloy, which allows for “unprecedented bit stability” despite the small grain size. The hope is that the greater density which HAMR allows will reduce the bill-of-materials, since fewer platters will be required for storing the same data.
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HAMR drives use pinpoint lasers in the write process. The heat temporarily lowers magnetic coercivity during the write process, after which the grains cool down to a magnetically stable state.
It’s hard to go it alone, so some manufacturers turn to platter specialists such as Resonac. Resonac was formed when Showa Denko K.K. and Showa Denko Materials Co. merged in early 2023. A leading manufacturer of next gen HAMR media, the firm uses thin films of Fe-Pt alloys, a powerful magnetic material that facilitates thermally stable small grains of magnetic crystals. Working out novel production methods to structure the magnetic layers, Resonac manufactures industry leading HD media with high magnetic coercivity.
Another key player in the HDD ecosystem is Intevac, which specializes in thin-film processing systems and other integral tools used in 65% of HDD manufacturing. Its systems, like the 200 Lean, are used to apply the magnetic layer over glass and aluminum disk substrates.
Toshiba and Western Digital have been behind Seagate in the HAMR race, which requires special platters that can withstand the heat. Through a collaboration that started as early as 2021, Toshiba has partnered with Resonac to create 30+TB drives using HAMR and MAMR (Microwave Assisted Magnetic Recording) technologies. Thomas Coughlin believes that Western Digital could also catch up with the HAMR trend by buying media from Resonac or other independent suppliers.
It’s All in the Pattern
Moving forward, expect to see more sophisticated substrates in the hard drive industry. As per the International Roadmap for Devices and Systems produced by the IEEE (Institute of Electrical and Electronics Engineers), each of the Big Three manufacturers – Seagate, Western Digital and Toshiba – will likely move to HAMR technology. And they won’t stop there. The IEEE predicts that by 2037, the big three will all make use of the mysterious “patterned heated dot media.”
The report says that patterned heated dot media consists of “discrete elements of the magnetic material distributed in an orderly fashion across the disk surface”. This new media will be used in conjunction with HAMR to allow an estimated 10Tpsi.
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When writing data, patterns matter. Shingled magnetic recording (SMR) is a way of writing on partly overlapping tracks. This increases write density, though write speed is generally slower.
How Shingled Magnetic Recording (SMR) Drives Up Data Center Capacity
HDD’s 3D Breakthrough?
Over a decade ago, when 3D NAND flash arrived on the scene, bringing speed, durability, and density. Now, researchers are focusing on making 3D magnetic media for HAMR HDDs. A proof-of-concept of this technology was carried out by the Japanese National Institute of Materials Research (NIMS), Tohoku University, and Seagate. The researchers produced a paper on the results in mid-2024.
The approach involves splitting the magnetic film on the disk into multiple levels. The magnetic grains are on a FePt-C (Iron Platinum-Carbon) nanogranular films. The layers of FePt-C have a spacing layer of Ru-C (Ruthenium-Carbon) in between. The idea is that by adjusting the temperature of the write head, you can change which FePt-C layer you write on.
TechXplorer provides a helpful breakdown on what this means. Simply put, in 3D HAMR, the top layer has a lower Curie temperature (the point at which the material loses its magnetic properties), while the bottom layer has a higher Curie temperature. This allows for the HAMR to locally heat the media over the Curie temperature, enabling multilevel recording and making the data writing process easier and more efficient. Potentially, this arrangement could support three or even four layers.
For his part, Thomas Coughlin thinks 3D HAMR could allow for 4Tbpsi storage density, potentially leading to 120TB HDDs. By comparison, Seagate’s platters currently have 1.5Tbpsi. Coughlin points out that the 3D HAMR idea has “been around for some time but it has never resulted in practical products.” His overall take seems to be one of cautious optimism, however.
Industry expert Chris Mellor points out that the write process would involve two passes: a high-temperature pass which writes the same bit to both layers, and a low-temperature pass modifying just the top layer. He believes this will lead to slower writes, though this could be overcome with dual actuators.
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3D NAND was a big jump forward for flash. Could 3D HAMR do the same for HDD?
Multiferroic, Ultra-Terrific
MIT has discovered a new material which could one-day change the game for the speed and energy efficiency of magnetic media. Researchers found a “multiferroic state” in an atomically thin material (nickel iodide). Roughly speaking, in “ferromagnets” the spin of electrons collectively align with a magnetic field, whereas in “ferroelectrics” the charge of electrons collectively align with an electric field. A multiferroic state is both ferroelectric and ferromagnetic.
So what? All known multiferroic materials were 3D, but the material MIT discovered is atomically-thin: 2D. In other words, it’s flat enough to stick on a platter. .
The researchers also managed to grow nickel iodide flakes, chilled them to 20K (-424°F), resulting in the first 2D multiferroic material. The challenge remains as to how these flakes can be miniaturized, and to test how quickly electric currents can switch bits in the flakes.
Here’s the gist: traditional HDDs use write heads with magnetic tips to reverse the magnetic polarity of electrons on a platter. The magnetic field at the tip of the write head is generated using an electric current, but doing that is time-consuming, energy-intensive, and generates heat. However, with multiferroic material you can reverse the polarity of the electrons directly using an electric current, thereby bypassing the need to generate a magnetic field with the write head.
“Having multiferroic properties in one material means that … it could save energy and time to write a magnetic hard drive”, explains MIT researcher Long Ju. “You could also store double the amount of information compared to conventional devices.”
Winning at Spinning
HDD platters are the bedrock upon which hard drive innovation is made. Whenever a company introduces a new magnetic recording technique, it is crucial to ensure the platter is up to the task. There’s no shortage of ideas, with platter innovations like dual-layer HAMR promising to lead HDD storage capacities to new heights. The future of HDDs seems bright, with HAMR media coming into its own just as HDD demand is surging.
However, technological advancements in media are only part of the puzzle. What matters most is cost-effectiveness. What effect will new platters have on drive prices, and how sensitive will they be to volatile supply chains? The future of HDD hinges on this question, since scaling production and maintaining the $/TB advantage over SSD remains essential.
Contact Horizon to see how you can procure cost-effective hard drives for all your data center needs.
