Hard disk drives (HDDs) and solid-state drives (SSDs) have taken different technology paths to storing data. HDDs use rotating magnetic disks to store and access data, while SSDs use integrated circuit assemblies and flash memory to store data electronically. This fundamental difference leads to major differences in performance and cost.
Currently, HDDs are significantly cheaper per gigabyte than SSDs. A 1TB HDD costs around $50 while a 1TB SSD costs around $100. However, the price gap has been narrowing over the past decade. In 2010, SSDs cost about 10 times more per gigabyte than HDDs. But with advances in flash memory density and manufacturing, along with increased market adoption, SSD prices have steadily declined.
Several factors influence storage costs for HDDs and SSDs, including component prices, manufacturing processes, supply and demand dynamics, technology improvements, power and speed capabilities, and reliability. As these factors evolve over time, they will determine whether SSDs can become more affordable than HDDs in the future.
Manufacturing Costs
There are key differences in the manufacturing costs for HDDs versus SSDs that contribute to the price differential between the two storage technologies. HDDs rely on physical platters, spindle motors, actuators, and read/write heads, while SSDs utilize NAND flash memory chips, controllers, and interconnects on a printed circuit board.
The raw materials for HDDs like aluminum, glass, and rare earth metals tend to be cheaper than the silicon and copper used for SSD NAND chips and PCBs. The factory equipment needed for HDD production like cleanrooms, platter sputtering machines, and mechanical component assembly is also generally less expensive. HDD production utilizes older, more commoditized fabrication processes compared to SSD fabs leveraging cutting-edge lithography [1].
Labor costs point to advantages for HDDs as well. The mechanical assembly of HDD components lends itself to automated mass production lines staffed by less specialized workers. SSD manufacturing requires more skilled labor for PCB population, chip packaging, and test. So while HDD fabrication may require more floor space, SSD fabs need more highly trained and expensive engineering talent.
Supply and Demand
The demand for traditional hard disk drives (HDDs) has been declining as solid-state drives (SSDs) gain market share. According to research, the client SSD market is expected to grow at a CAGR of 20-31% from 2024-2031, while the HDD market shrinks. As SSDs become more ubiquitous and gain economies of scale, their manufacturing costs decline, making them more affordable. With lower prices, more consumers and businesses are choosing SSDs over HDDs for their speed, durability, and energy efficiency.
SSD shipments have grown from around 100 million units in 2011 to over 500 million units in 2021. Meanwhile, HDD shipments peaked at about 650 million units in 2015 and have declined to around 350 million units in 2021 according to industry analysis. As manufacturing scales up, SSD prices are projected to become even more competitive with HDDs. The outlook shows SSD capturing 50% or more of the overall storage market in terms of exabytes shipped within the next few years.
Technology Improvements
SSDs continue to improve their density through advances like 3D NAND. By stacking NAND memory cells vertically, 3D NAND allows for higher capacities in a smaller space. Major manufacturers like Samsung, SK Hynix, and Micron have transitioned to 96-layer and 128-layer 3D NAND, with prospects of increasing to over 200 layers (AnandTech, 2021). This stacking expands capacity per chip, reducing cost-per-gigabyte.
HDDs are also incorporating new technologies to improve aerial density. Shingled magnetic recording (SMR) overlaps tracks to pack more data in the same area. Heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) use external energy to write to high stability medium. Seagate plans to release HAMR drives starting with 32 TB in 2023, scaling up to 40 TB and higher (Tom’s Hardware, 2022). Western Digital has a 26 TB SMR drive planned for 2022 and HAMR drives slated for 2024/2025 (Blocks & Files, 2022).
Data Density
SSDs lack moving parts like disk platters and read/write heads, allowing the flash memory chips to be packed more densely. This gives SSDs an inherent advantage in data density over traditional HDDs. According to Western Digital, HDD areal density growth has slowed in recent years, sitting around 1.1 Tbit/inch2 for the past several years.
As noted by Tom’s Hardware, “The rapid increase in HDD capacity is largely thanks to the number of platters inside the drive rather than areal density improvements. While higher platter counts enable higher overall capacities, it also reduces performance.”
In contrast, the small form factor of flash memory chips enables SSDs to continue improving in data density. Forbes predicts SSD density will improve at a 22% CAGR through 2030. So while HDD areal density stagnates, SSDs are on a trajectory to surpass them. Higher data density directly translates to lower cost per GB of storage.
Sources:
https://blog.westerndigital.com/explained-hdd-areal-density/
https://www.forbes.com/sites/tomcoughlin/2022/09/18/we-need-a-boost-in-hdd-areal-density/
Power and Thermal
SSDs have a lower power consumption than HDDs. According to research from Scality, SSDs have a power draw ranging from 5 to 20 watts, compared to HDDs which range from 5.7 to 9.4 watts (Source). SSDs using less power allows for more compact and efficient system designs, with lower cooling requirements.
On Reddit, users also report SSDs being much more power efficient than HDDs, with some estimating SSDs use less than 10% of the power consumption of a comparable HDD (Source). The lower power draw of SSDs is a key advantage over traditional hard drives.
Interface Speeds
SSDs can utilize faster interfaces like PCIe which offers significant performance advantages over SATA. For example, an NVMe PCIe SSD can achieve sequential read speeds over 3,500 MB/s compared to around 550 MB/s for a SATA SSD. This is due to PCIe operating at higher bandwidths with lower latency and parallelism.
In contrast, HDDs are limited by their mechanical nature so latency remains relatively high even with SATA interfaces. The physical spinning disks and moving heads bound their maximum performance. While HDDs can reach around 200 MB/s, their average response times are much slower than SSDs.
Overall, the interface plays a big role in SSD vs HDD performance. By removing the mechanical bottleneck, SSDs can better leverage cutting-edge interfaces like PCIe for substantially faster speeds.[1]
Reliability
SSDs tend to be more reliable than HDDs because they have no moving parts. HDDs rely on spinning platters and moving read/write heads, which makes them more prone to mechanical failures over time. According to Backblaze’s 2022 HDD failure statistics, failure rates for HDDs tend to increase each year. After 4 years, over 10% of HDDs had failed. In comparison, failure rates for SSDs have stayed consistently low, around 1% per year.
According to Backblaze, SSD annual failure rates have remained steady at around 1% over multiple years of data. In their Q1 2023 report, the overall failure rate for SSDs was just 0.92%. Comparatively, for HDDs the failure rate was 2.2% for 4 year old drives and 10.2% for 6 year old drives (Backblaze).
With no moving components and consistent low failure rates over time, SSDs are clearly the more reliable storage option versus HDDs which see increasing failures as the drives age.
Outlook
SSD prices are expected to continue falling at a faster rate than HDD prices going forward. This is due to improvements in NAND flash manufacturing processes as well as economies of scale as SSDs become more mainstream. Most industry analysts predict that SSD costs per GB will fall below HDD costs per GB at some point in the next 5 years.
According to a Reddit analysis of historical pricing trends, SSD and HDD costs per GB could reach parity by 2025 for high capacity drives. However, the crossover point for lower capacity SSDs vs. HDDs may come even sooner, potentially by 2023.
The exact timing of the price crossover is difficult to predict and will depend on many factors. But the overall trajectory is clear – SSD pricing will continue to decline rapidly while HDD pricing declines more slowly. This cost advantage, combined with the performance and reliability benefits of SSDs, point to SSDs eventually displacing HDDs for most storage applications in the future.
Conclusions
To sum up, the key factors influencing the relative costs between SSDs and HDDs are manufacturing processes, supply and demand dynamics, technological improvements, and economies of scale. SSDs are currently more expensive in terms of dollar per gigabyte costs, but the gap has been narrowing over time.
Based on the ongoing improvements in 3D NAND flash technology, SSD manufacturing processes, higher production volumes, and expected gradual declines in HDD demand, projections indicate that SSD $/GB could reach parity with HDD around 2023-2025. However, fluctuations in supply and demand could impact the exact crossover point. Overall, the outlook is that SSDs will continue on a steady path to matching and eventually beating HDD $/GB costs within the next 3-5 years.