We are now in the age of petabyte-scale enterprise data, and it won’t stop. Data centers have a clear job: either scale up their storage or fall behind. This is because of AI pipelines, the Internet of Things (IoT), compliance logging, and analytics. However, businesses face a harsh economic reality as they create, store, and reprocess more warm-tier data than ever.
Regarding performance, flash storage is the most talked about, but it’s not the most important part of infrastructure. Hard disk drives (HDDs) still do that job, and it’s not just because of old habits. Western Digital says that enterprise HDDs are still 6x cheaper per terabyte than enterprise SSDs, and this gap is not expected to get any smaller over at least the next five years.
Brad Warbiany, Director of Planning & Strategy at Western Digital, explains, “The cost advantage of HDDs comes from their ability to deliver storage at a much lower production cost per bit.” Flash is great for certain tasks, but it can’t compete economically with HDDs for warm data. This article explores why HDDs remain essential for modern infrastructure growth, and how Western Digital’s specialized technologies — such as UltraSMR, HelioSeal®, and ePMR — are redefining the possibilities of long-term storage.
Quantifying the Data Surge
To understand why storage strategy must evolve, we first need to examine how enterprise data is actually structured and how its access patterns are shifting.
The Shape of Modern Data
Statista says that as of 2024, the world will have made, captured, copied, and used 149 zettabytes of data. That number will be more than 394 zettabytes by 2028. But it’s not just the volume, it’s the composition. A small slice of enterprise data is hot, requiring low-latency access. A separate tier is cold, rarely touched. However, most enterprise storage sits in the warm tier, which is frequently accessed but not latency-critical.
“Think about a social media post,” Brad explains. “It’s hot for a week or two, then becomes warm. You still want it instantly retrievable a year later, but you’re not touching it every day.” This dynamic reflects what’s happening across AI training datasets, log archives, and cloud content delivery: data doesn’t get deleted, it just cools. And warm data is growing faster than any other category.
What This Means for Infrastructure
Enterprises trying to scale using SSDs for warm data are paying a premium they don’t need to. Brad elaborates, “Warm-tier workloads don’t require SSDs’ performance, and the cost-to-benefit ratio simply breaks at scale.”
The Economics of Scale: HDD vs. SSD TCO
That economic gap becomes clearer when we examine the long-term cost trends, starting with the cost per terabyte and how it will evolve over time.
Cost per Terabyte Today and Through 2027
Western Digital’s internal modeling and external analyst forecasts show that HDDs offer a 6x cost-per-terabyte advantage over SSDs, with no near-term convergence in sight. This projection accounts for technological improvements in both media types, but also reveals their limitations.
“Bit density is the limiter,” Brad notes. “We’ve tracked HDD vs. SSD economics since 2015, and despite innovation on both sides, the annual cost-per-terabyte decline has remained nearly identical. They’re tracking parallel paths. When we look at the technology arcs going forward with increased 3D layer counts as well as QLC and possibly PLC on the SSD side, and HAMR followed by HDMR on the HDD side, we believe they will continue to track on parallel paths.”
The key takeaway? SSDs may get cheaper, but so do HDDs, and the price delta remains wide. Whether it’s 5x or 7x five years from now, HDD’s advantage will persist.
Why SSD TCO Doesn’t Scale for Warm Data
Flash excels in high-IOPS, random-access environments. However, as Brad points out, “Applying SSD to warm data is like using a sports car to move to a new house across town rather than a moving truck.” Warm-tier storage, like backup, media repositories, and training datasets, doesn’t require the microsecond access that SSDs deliver. So why pay for it?
The result: enterprises that misalign workloads with storage mediums end up with an inflated total cost of ownership (TCO) and limited return on storage investment. And that unnecessarily inflated investment carries an opportunity cost — that is investment that could have been spent on other important priorities.
Hidden Cost Drivers: Power, Cooling, and Density
There’s a common misconception that SSDs are always more power-efficient — a narrative often emphasized by SSD proponents. However, Brad clarifies that this power efficiency is marginal in enterprise contexts and rarely changes the overall economics. “Enterprise SSDs don’t benefit from the low-power idle states consumer SSDs use,” he says. “In real-world use, the idle power of enterprise SSDs can be almost the same as that of HDDs. SSDs’ active power, in fact, can be higher than HDDs, often as high as 25 W in high-performance workloads. And let’s face it — you don’t buy an expensive SSD for it to sit idle.”
While these small power savings may exist, they are an order of magnitude smaller than the substantial acquisition cost gap. TCO is overwhelmingly driven by price per TB — and that’s where HDDs remain unmatched.
Western Digital’s Purpose-Built HDD Portfolio
To meet the demands of modern workloads and petabyte-scale environments, Western Digital has engineered a portfolio that is purpose-built for warm-tier efficiency and long-term scalability.
Designed for the Data-Heavy Enterprise
The Western Digital Ultrastar® DC HC600 series exemplifies the scale-ready design modern infrastructure demands. With models up to 32TB and a roadmap that includes 11-disk platforms, this series is engineered for software-defined, object, and distributed storage environments.
From hyperscale cloud providers to AI-driven research facilities, these drives enable more data per rack, per watt, and per dollar.
Technologies That Drive TCO Efficiency
Western Digital’s HDD innovation targets one metric: TCO. Key advancements include:
- UltraSMR: Extends track density to deliver up to 20% more capacity than conventional magnetic recording. “Same power, same cooling, more bits — that’s pure TCO improvement,” Brad emphasizes.
- HelioSeal: Helium instead of air enables lower internal friction and higher platter counts. This innovation improves efficiency and also allows for denser, cooler, and more reliable drives.
- ePMR, OptiNAND, and ArmorCache: These enhancements boost sequential write performance and improve metadata handling, helping warm-tier workloads like backup, log ingestion, and content staging perform faster and last longer.
Brad says, “We’re optimizing for capacity and reliability, not just speed. These technologies keep us ahead in the areas that matter most for petabyte-scale deployments.”
Real-World Impacts and Case Studies
The value of HDDs isn’t just theoretical; it’s proven every day in some of the world’s largest and most demanding environments. In fact, the majority of global cloud and enterprise storage architectures rely on HDDs for warm data, thanks to their compelling TCO, reliability, and scalability. For organizations with petabyte- and exabyte-scale storage needs, optimizing the right tier for the right workload can unlock significant and immediate cost savings, while improving efficiency and sustainability.
1 One TB is equal to one trillion bytes. Actual user capacity may be less due to the operating environment.
Hyperscaler Adoption
The adoption of SMR HDDs by one of the top cloud storage providers, including the Ultrastar DC HC600 series, has resulted in a 20% cost reduction in storage without compromising data availability or throughput. “This isn’t a corner case,” Brad says. “This is how hyperscalers build for scale.”
Most global hyperscale storage architectures, whether proprietary or software-defined, use HDDs as the foundation for warm-tier scale.
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Strategic Guidance for Storage Decision-Makers
With the economics and use cases clearly established, the next step is helping IT leaders make more intelligent, more sustainable storage decisions at scale.
Not All Data Is Equal, So Don’t Store It That Way
A blanket SSD approach is unsustainable. Smart infrastructure leaders segment by workload:
- Hot tier: SSDs for latency-critical tasks
- Warm tier: HDDs for scale and sustainability
- Cold tier: Tape or archival platforms
This model ensures performance where needed, while optimizing cost across the full storage footprint.
Build for Tomorrow, Not Just Today
With AI, analytics, and compliance archiving driving exponential data growth, flash-only infrastructure becomes a financial liability. Western Digital’s roadmap includes technologies like HAMR (heat-assisted magnetic recording) to continue increasing area density and lowering cost per terabyte. Brad says, “HAMR is our next major inflection point, built for the warm tier.”
Conclusion: Build Smarter, Scale Efficiently
Enterprise data isn’t just growing, it’s compounding. But scaling your infrastructure doesn’t have to mean scaling your spend. HDDs offer a proven, cost-effective path forward for most data warm-tier workloads that are accessed regularly but that don’t require flash-level performance.
Western Digital’s purpose-built HDD platforms, backed by innovations like UltraSMR, HelioSeal, ePMR, and now HAMR, are engineered specifically for this challenge. They reduce cost per terabyte, cut power consumption, and simplify scaling, all without compromising reliability or availability.
Brad Warbiany says it best: “The economics of HDDs aren’t just compelling, they’re foundational. That’s why enterprise architects rely on them, and why the 6x TCO advantage continues to drive decision-making at scale.”
If you’re planning for sustainable, petabyte-level growth, stop asking if HDDs are still relevant and ask how soon you can start migrating the right workloads to the right tier.
Ready to optimize your infrastructure? Explore the Western Digital Ultrastar DC HC600 series and see how your warm-tier strategy could start saving you money today.