Seagate and Western Digital Shares Fall as Toshiba Plans HDD Expansion
Shares of Seagate Technology (NASDAQ: STX) and Western Digital (NASDAQ: WDC) fell sharply on October 2 after a report that Toshiba plans to substantially expand its hard disk drive (HDD) manufacturing capacity for artificial intelligence data centers.
Seagate fell roughly 11% in early trading, while Western Digital declined about 7%, according to market reports. The selling came despite a broader technology market that was holding up better, suggesting that investors were responding specifically to the potential impact of additional HDD supply rather than abandoning the broader AI infrastructure theme.
The catalyst was a Nikkei report that Toshiba plans to invest about ¥60 billion, or roughly $380 million, to double its HDD production capacity by fiscal 2027. The expansion is expected to center on Toshiba's manufacturing facility in the Philippines.
For investors, the important question is whether Toshiba's additional capacity could weaken the supply constraints that have helped Seagate and Western Digital raise prices and expand margins during the AI-driven storage boom.
Why Seagate and Western Digital stocks are falling
The market reaction is largely about future supply, not a sudden deterioration in current HDD demand.
For much of 2026, Seagate and Western Digital have benefited from strong demand for high-capacity storage from cloud providers and AI data centers. Limited HDD supply has allowed the two major U.S. manufacturers to maintain pricing power while customers have continued increasing storage purchases.
Toshiba's expansion introduces a different possibility: more competing capacity could eventually give large cloud customers additional negotiating leverage.
According to the Nikkei report, Toshiba currently has just over 10% of the HDD market by storage capacity and wants to increase that share to 30% over the medium term. If that ambition were achieved, Toshiba would become a much more significant competitor to Seagate and Western Digital.
That does not mean the market will suddenly become oversupplied. Toshiba's planned capacity still has to be built, qualified and absorbed by customers. But investors are already looking ahead because the current valuations of Seagate and Western Digital reflect exceptionally strong expectations for the storage cycle.
Toshiba is targeting the same AI storage opportunity
The irony of the announcement is that Toshiba's expansion is itself evidence of how attractive the AI storage market has become.
AI data centers generate enormous amounts of information that must be stored. While high-performance solid-state drives (SSDs) are important for fast-access workloads, HDDs remain attractive for large volumes of lower-cost, high-capacity data.
That makes high-capacity HDDs particularly relevant as cloud operators expand AI infrastructure.
Toshiba reportedly plans to add production lines capable of making drives with up to 40% higher per-unit capacity, with plans for mass production of 65-terabyte-class HDDs by 2030 and an eventual target of 100-terabyte-class products.
The expansion therefore isn't simply about producing more conventional drives. Toshiba is attempting to compete for the higher-capacity storage market that has become increasingly important to AI infrastructure.
Seagate and Western Digital have strong fundamentals
The stock decline should be viewed against the companies' recent financial performance.
Seagate finished fiscal 2026 with $12.195 billion of revenue, up 34% year over year. Fourth-quarter revenue reached $3.629 billion, while GAAP gross margin rose to 52.3% from 37.4% a year earlier. Seagate also generated a record $3.1 billion of free cash flow during fiscal 2026, according to the company's results.
Western Digital reported similarly strong numbers. Fiscal fourth-quarter revenue increased 44% to $3.75 billion, while GAAP gross margin reached 54.1%. The company generated $1.39 billion of operating cash flow and $1.28 billion of free cash flow during the quarter.
Western Digital also expects fiscal first-quarter 2027 revenue of approximately $4.1 billion, plus or minus $100 million, with non-GAAP gross margin of 55% to 56%.
These figures indicate that the current business remains strong. The concern is what happens when additional competitor capacity eventually reaches the market.
AI demand remains a major support for HDDs
The Toshiba announcement does not eliminate the fundamental demand story.
Western Digital's fiscal fourth-quarter presentation showed that cloud revenue represented 89% of total revenue in the quarter. The company has increasingly positioned its business around hyperscalers, cloud providers and data-intensive workloads.
Seagate has also linked its growth outlook directly to AI-driven data creation and cloud storage demand. Its latest full-year results highlighted strong cloud data-center demand and the company's Mozaic HAMR technology roadmap.
HAMR, or heat-assisted magnetic recording, is a technology designed to increase the amount of data that can be stored on a hard-drive platter. Seagate says its latest Mozaic 4+ platform supports drives of up to 44TB and is already qualified and in production with two hyperscale cloud providers.
This technology race could become increasingly important if the industry moves from simply adding capacity to competing on storage density, power efficiency and total cost per terabyte.
The real risk is pricing power
The biggest issue for Seagate and Western Digital is not necessarily losing customers overnight.
The more immediate risk is pricing power.
When HDD supply is constrained, manufacturers can negotiate from a stronger position. Customers have fewer alternatives, and suppliers can prioritize higher-value products.
More Toshiba capacity could gradually change that balance.
If supply grows faster than demand, cloud customers could gain leverage during contract negotiations. That could slow average selling price growth, compress gross margins or make it harder for Seagate and Western Digital to maintain the exceptional profitability they have recently achieved.
The timing matters as well. Toshiba's announced expansion is aimed at fiscal 2027, meaning investors may be pricing in a potential future supply increase well before the full capacity is actually available.
Why the impact may take time
There is an important distinction between announced capacity and commercially available capacity.
A new HDD production line requires construction, equipment installation, qualification, manufacturing ramp-up and customer acceptance. Enterprise and hyperscale customers also tend to have demanding reliability and qualification requirements.
That means Toshiba's expansion is unlikely to instantly flood the market.
Seagate and Western Digital also have established relationships with major cloud customers and their own technology roadmaps. Western Digital has entered fiscal 2027 with strong revenue visibility, while Seagate continues expanding its high-capacity HAMR portfolio.
Consequently, the ultimate impact will depend on how quickly Toshiba scales and whether overall AI-driven storage demand grows rapidly enough to absorb the new supply.
The stocks had already rallied sharply
Another factor behind the intensity of Friday's move is the enormous gains these stocks had already recorded.
Reports indicated that Seagate had gained more than 200% year to date before the selloff, while Western Digital had risen more than 140%.
When a stock has experienced such a large rally, investors often become more sensitive to information that could challenge the assumptions behind its valuation.
That can produce a much larger reaction than the underlying fundamental change might initially suggest.
In other words, Friday's decline does not by itself establish that the HDD cycle has ended. It shows that investors are reassessing how long the current combination of tight supply, strong AI demand and elevated pricing can persist.
What investors should watch next
For Seagate and Western Digital, several indicators will be particularly important over the coming quarters:
The speed at which Toshiba's additional Philippine capacity comes online
Actual HDD demand from hyperscale and AI data-center customers
Average selling prices for high-capacity drives
Gross-margin trends at Seagate and Western Digital
Customer contract volumes and long-term supply agreements
Adoption of higher-capacity HAMR products
Capital spending by major cloud providers
Whether AI-driven storage demand grows faster than new HDD supply
Investors should also distinguish between unit demand and storage capacity demand. Even if the number of HDDs shipped does not rise dramatically, increasing capacity per drive can allow total stored data to grow substantially.
That dynamic could help the industry absorb additional manufacturing capacity without creating an immediate glut.
What the Toshiba expansion means for the HDD industry
The development ultimately creates a more complicated picture for the storage sector.
For Toshiba, the investment is an attempt to capture a larger share of a market benefiting from AI infrastructure spending. For Seagate and Western Digital, it introduces a potentially important new source of competition.
But the expansion also confirms that the industry's demand outlook is strong enough to justify significant new investment.
The long-term outcome will therefore depend on a race between storage demand growth and manufacturing capacity growth.
If AI-generated data continues expanding rapidly, the market may be able to absorb Toshiba's additional output. If capacity expands faster than demand, pricing and margins could come under pressure.
Conclusion
Seagate and Western Digital shares fell sharply after reports that Toshiba plans to double its HDD production capacity by fiscal 2027 through an approximately ¥60 billion investment in the Philippines.
The selloff reflects concerns that additional Toshiba capacity could eventually weaken the tight supply conditions that have supported pricing power and strong margins for the two leading U.S. HDD manufacturers.
At the same time, Seagate and Western Digital enter the period with strong financial results, significant exposure to cloud storage and technology investments aimed at higher-capacity AI workloads.
The key issue for investors is therefore not simply whether Toshiba expands production, but whether global AI and cloud storage demand grows quickly enough to absorb that new capacity without materially weakening HDD pricing.
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This article is for informational and educational purposes only and should not be considered investment advice.