Seagate, Western Digital Slide on Toshiba HDD Plan

Seagate (STX) and Western Digital (WDC) fell about 10% after Nikkei reported Toshiba will double hard-disk output, hitting two of 2026's top AI stocks.

Lead

Shares of Seagate Technology (NASDAQ: STX) and Western Digital (NASDAQ: WDC) fell sharply on Friday, October 2, after Nikkei reported that Toshiba plans to double its hard-disk-drive production capacity. Seagate lost $96.58 to $848.99, and Western Digital shed $47.27 to $415.29, both down roughly 10% in the session. The selloff came as the broader market rose, with the Invesco QQQ Trust (QQQ) up 1.17% to $750.73.

What Did Nikkei Report About Toshiba's Plan?

Nikkei reported that Toshiba will invest about ¥60 billion, or roughly $400 million, to double its hard-disk-drive capacity by fiscal 2027. The expansion centers on the company's factory in the Philippines and targets demand for data storage from AI infrastructure.

Toshiba holds just over 10% of the hard-disk market, measured by storage capacity. The company's medium-term goal is a 30% share. Reaching it would require taking volume from the two U.S. leaders, which together with Toshiba make up the industry.

Why Did Seagate and Western Digital Fall So Sharply?

The stocks fell hard because both had run far ahead of the market, leaving little room for any news that threatened pricing. Seagate had risen about 210% in 2026 and Western Digital about 150%, which made them two of the strongest AI stocks of the year. Their gains rested on a tight supply market in which drive makers held pricing leverage and kept unit volumes restrained.

A rival promising to double output challenges that premise. Western Digital's chief executive has described the supply environment as very tight, giving the company room to raise prices. A larger Toshiba would erode that advantage if the added capacity reached customers.

The reaction was confined to hard-drive makers. The Roundhill Memory ETF (DRAM) rose 0.82% to $62.54, and flash-storage maker SanDisk (SNDK) slipped about 1.8%. Micron, SK Hynix and other memory names were largely unaffected, which points to a company-specific repricing rather than a sector retreat.

Does Toshiba's Expansion Threaten the Hard-Drive Supply Squeeze?

Not immediately, and the constraints on Toshiba are real. Unlike Seagate and Western Digital, Toshiba relies on outside suppliers for key components, including recording media and read-write heads. Those suppliers would also need to expand sharply for Toshiba to double output, which limits how much new capacity can reach the market and how fast.

The timeline also matters. Capacity targeted for fiscal 2027 would arrive well after current contract pricing is set. Hyperscale customers, the largest buyers of high-capacity drives, typically commit to supply agreements well in advance. That gives the incumbents time to defend share and pricing.

Strategic Context

The episode shows how crowded positioning has become in storage stocks tied to AI data-center buildouts. Hard drives hold the bulk of the vast data volumes that AI training and archiving generate, and demand has outrun supply. A single report that could add supply was enough to trigger a double-digit decline in each stock.

For Toshiba, a $400 million investment is modest next to the market capitalization erased at its competitors. The size of that gap between the spending and the selloff shows how much future scarcity was already priced into Seagate and Western Digital.

Outlook

Toshiba's expansion is a medium-term supply risk, not a near-term one, given its dependence on component suppliers and a fiscal 2027 horizon. Seagate and Western Digital still carry large 2026 gains, and the next test will be whether they hold pricing in upcoming contract cycles and what they say about capacity plans at their next earnings reports. Any sign that Toshiba's suppliers are adding media and head capacity would be the clearest signal that the supply squeeze is easing.