Question:

How do the historical and projected trends of hard disk drive (HDD) capacity growth inform the feasibility of achieving 40TB or 200TB HDDs by 2040? What are the main factors and challenges that influence the HDD capacity expansion?.

Answer:

Hard disk drives (HDDs) are data storage devices that use magnetic disks to store and retrieve data. HDDs have been widely used in computers and other electronic devices for decades, and have seen remarkable improvements in their capacity, performance, and reliability. However, as the demand for data storage continues to grow exponentially, HDDs face increasing challenges to meet the future needs of consumers and enterprises. In this article, we will examine the historical and projected trends of HDD capacity growth, and discuss the feasibility of achieving 40TB or 200TB HDDs by 2040. We will also explore the main factors and challenges that influence the HDD capacity expansion, and the potential solutions and alternatives.

Historical and Projected Trends of HDD Capacity Growth

HDD capacity growth has followed a general trend of doubling every two to three years, which is often referred to as Kryder’s Law. This trend has been driven by various technological innovations, such as perpendicular magnetic recording (PMR), shingled magnetic recording (SMR), and helium-filled drives, that have increased the areal density (the amount of data that can be stored on a unit area of a disk) and the number of platters (the circular disks that store data) in a HDD. According to IDC, the average capacity per drive increased at a five-year compound annual growth rate (CAGR) of 25.5% from 2020 to 2025 .

Based on this trend, some analysts have projected that HDDs could reach 40TB by 2026 and 200TB by 2033. However, these projections are based on optimistic assumptions and do not account for the physical and economic limitations that HDDs face. As HDDs approach the fundamental limits of magnetic recording, the rate of capacity growth is expected to slow down significantly. Moreover, the cost per terabyte of HDDs may not decrease as fast as the capacity increases, making HDDs less competitive with other storage technologies, such as solid-state drives (SSDs).

Factors and Challenges that Influence the HDD Capacity Expansion

There are several factors and challenges that influence the HDD capacity expansion, both from the supply and demand sides. On the supply side, HDD manufacturers have to overcome the technical barriers and the high research and development (R&D) costs associated with increasing the HDD capacity. On the demand side, HDD customers have to balance the trade-offs between capacity, performance, reliability, and cost, and consider the suitability of HDDs for different applications and environments.

Some of the major technical barriers that HDD manufacturers face are:

• The superparamagnetic limit: This is the limit at which the magnetic grains on a disk become too small and unstable to store data reliably. HDDs have been approaching this limit for years, and have relied on various techniques, such as PMR and SMR, to increase the areal density. However, these techniques have their own drawbacks, such as reduced write performance and increased complexity. To overcome this limit, HDD manufacturers are developing new recording technologies, such as heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR), that use external energy sources to write data on smaller and more stable grains. However, these technologies are still in the early stages of commercialization, and face challenges such as high power consumption, high temperature, and high wear and tear .
• The mechanical limit: This is the limit at which the mechanical components of a HDD, such as the actuator arm, the read/write head, and the spindle motor, become too fast and precise to operate reliably. HDDs have been increasing the rotational speed and the track density (the number of tracks per inch on a disk) to improve the performance and the capacity. However, these improvements also increase the mechanical stress and the vibration on the HDD, and require more sophisticated control and calibration systems. To overcome this limit, HDD manufacturers are developing new mechanical designs, such as two-dimensional magnetic recording (TDMR) and multi-actuator drives, that use multiple read/write heads and actuators to access data on a disk. However, these designs also increase the complexity and the cost of the HDD, and face challenges such as interference, synchronization, and compatibility .
• The physical limit: This is the limit at which the physical size and weight of a HDD become too large and heavy to fit and function in a given device or system. HDDs have been increasing the number of platters and the form factor (the size and shape of a HDD) to increase the capacity. However, these increases also affect the power consumption, the heat dissipation, and the shock resistance of the HDD, and limit the number of HDDs that can be installed in a device or system. To overcome this limit, HDD manufacturers are developing new physical designs, such as helium-filled drives and glass substrates, that reduce the air resistance and the thickness of the platters, and allow more platters to be stacked in a HDD. However, these designs also increase the manufacturing difficulty and the cost of the HDD, and face challenges such as sealing, leakage, and durability .

Some of the major economic factors that HDD manufacturers and customers face are:

• The R&D cost: This is the cost of developing and implementing new technologies and designs to increase the HDD capacity. HDD manufacturers have to invest heavily in R&D to overcome the technical barriers and to maintain their competitive edge in the market. However, the R&D cost is also affected by the market demand and the profitability of the HDD business. If the demand for HDDs declines or the profit margin shrinks, the R&D cost may become unsustainable or unprofitable for the HDD manufacturers, and may discourage them from pursuing further capacity expansion .
• The cost per terabyte: This is the cost of storing one terabyte of data on a HDD. HDD customers have to consider the cost per terabyte of HDDs in relation to their storage needs and budgets, and compare it with the cost per terabyte of other storage technologies, such as SSDs. HDDs have traditionally been cheaper than SSDs in terms of cost per terabyte, and have been preferred for high-capacity and low-performance applications, such as backup, archive, and cold storage. However, SSDs have been decreasing their cost per terabyte faster than HDDs, and have been gaining market share in high-performance and low-capacity applications, such as boot, cache, and hot storage. Moreover, SSDs have advantages over HDDs in terms of performance, reliability, power consumption, and form factor, which may offset the cost difference in some cases. Therefore, HDDs may face increasing competition and pressure from SSDs, especially in the enterprise and mobile segments, and may have to lower their cost per terabyte to remain viable .

Feasibility of Achieving 40TB or 200TB HDDs by 2040

Given the above factors and challenges, the feasibility of achieving 40TB or 200TB HDDs by 2040 is uncertain and depends on several assumptions and scenarios. Some possible scenarios are:

• Optimistic scenario: In this scenario, HDD manufacturers successfully overcome the technical barriers and develop new recording, mechanical, and physical technologies and designs that enable significant increases in the areal density, the number of platters, and the form factor of HDDs. HDD customers have strong and sustained demand for high-capacity and low-cost HDDs, especially in the cloud and data center segments, and are willing to pay a premium for the latest HDD technologies and designs. HDDs maintain their cost advantage over SSDs, and coexist with SSDs in a hybrid storage environment. In this scenario, HDDs could reach 40TB by 2026 and 200TB by 2033, as projected by some analysts.
• Pessimistic scenario: In this scenario, HDD manufacturers face difficulties and delays in overcoming the technical barriers and developing new recording, mechanical, and physical technologies and designs that enable significant increases in the areal density, the number of platters, and the form factor of HDDs. HDD customers have weak and declining demand for high-capacity and low-cost HDDs, especially in the enterprise and mobile segments, and are reluctant to pay a premium for the latest HDD technologies and designs. HDDs lose their cost advantage over SSDs, and are replaced by SSDs in most storage applications. In this scenario, HDDs could reach 40TB by 2030 and 200TB by 2040, or never reach these capacities at all.
• Realistic scenario: In this scenario, HDD manufacturers partially overcome the technical barriers and develop some new recording, mechanical, and physical technologies and designs that enable moderate increases in the areal density, the number of platters, and the form factor of HDDs. HDD customers have moderate and fluctuating demand for high-capacity and low-cost HDDs, depending on the application and the environment, and are sensitive to the price and the performance of the latest HDD technologies and designs. HDDs narrow their cost gap with SSDs, and coexist with SSDs in a tiered storage environment. In this scenario, HDDs could reach 40TB by 2028 and 200TB by 2038, or slightly later.

Conclusion

HDDs

are data storage devices that have seen remarkable capacity growth over the years, but also face increasing challenges to meet the future needs of data storage. The feasibility of achieving 40TB or 200TB HDDs by 2040 is uncertain and depends on several factors and challenges, both from the supply and demand sides. HDD manufacturers and customers have to balance the trade-offs between capacity, performance, reliability, and cost, and consider the suitability of HDDs for different applications and environments. HDDs may have to compete and cooperate with