The AI storage trade just got a reality check.
Sandisk and Western Digital delivered strong quarterly numbers, but investors were looking for something even bigger.
That is the key takeaway from Thursday’s selloff across storage and memory stocks.
Sandisk fell sharply in premarket trading, while Western Digital also dropped heavily. The weakness spread across the sector, with Seagate, Micron, SK Hynix, Intel, AMD and Marvell also trading lower.
The reaction says a lot about where expectations have moved in the AI trade. When stocks have already rallied aggressively, simply beating earnings estimates may no longer be enough.
The numbers were actually strong
Western Digital reported a solid fiscal fourth quarter.
- Adjusted earnings rose to $3.56 per share, beating estimates of $3.29
- Revenue jumped 44% year over year to $3.75 billion
- Cloud revenue climbed 43% to $3.3 billion
- Gross margin expanded to 54.4%
- Operating income surged 126% to $1.66 billion
- Free cash flow reached $3.5 billion for fiscal 2026
The company also returned $3.1 billion to shareholders through dividends and share repurchases.
So this was not a weak earnings report.
The problem was the gap between good results and what investors had already priced in.
Sandisk faced the same problem
Sandisk has been one of the biggest winners in the storage boom this year, rising more than fivefold before Thursday’s decline.
Its business is benefiting from the huge amount of storage needed to support AI data centers. Data center revenue rose more than 400% in 2026 compared with 2025, while quarterly data center revenue doubled from the previous quarter.
But the market was focused on what comes next.
Sandisk expects fiscal first-quarter revenue of $10.3 billion to $10.8 billion, below the roughly $11.16 billion analysts were expecting.
That was enough to trigger a sharp reaction.
The message from investors was simple: strong growth is expected. The question is whether growth can keep beating an already extremely high bar.
Why expectations matter so much now
The AI boom has transformed memory and storage companies into some of the market’s hottest trades.
Demand for high-end memory remains strong, while AI data centers continue to require enormous amounts of storage.
That has helped push chip prices higher and boosted earnings across the industry.
But the stocks have also moved much faster.
Sandisk has gained more than fivefold this year. Western Digital has more than tripled. Both have significantly outpaced the broader semiconductor index and the S&P 500.
That creates a different investment environment.
When a stock has already priced in years of strong growth, investors start looking for evidence that the business can keep exceeding expectations, rather than simply meeting them.
The bigger question: can AI demand stay this strong?
For now, the underlying demand story still looks healthy.
Western Digital expects fiscal first-quarter revenue of about $4.1 billion, with a range of $4.0 billion to $4.2 billion.
Management continues to see demand from AI training, AI inference, agentic AI and physical AI workloads.
One particularly important point is that around 80% of hyperscale data center data is still stored on hard disk drives, largely because of their cost, scalability and power-efficiency advantages.
Western Digital is also moving forward with higher-capacity drives.
The company expects to launch its 44TB HAMR hard drive in the first half of 2027, while its next-generation 40TB EPMR drives have already begun shipping.
That suggests the storage opportunity is not disappearing.
But margins could become the next debate
This is where investors may become more cautious.
Sandisk’s gross margin reached a record 84.6% in its latest quarter. Its fiscal 2027 guidance calls for gross margin of 83% to 85%.
That is still extremely strong.
But when margins and pricing have risen sharply, investors naturally start asking whether they are close to a peak.
RBC Capital Markets also pointed to moderating price growth and the possibility that margins may be near their highs.
That does not mean the AI storage story is over.
It means the market may be entering a phase where execution matters more than the headline AI narrative.
The selloff is bigger than Sandisk and Western Digital
The reaction quickly spread through the broader chip sector.
- Seagate fell
- Micron declined
- SK Hynix dropped
- AMD traded lower
- Intel slipped
- Marvell also weakened
That makes Thursday’s move worth watching.
Investors are not necessarily questioning whether AI data centers need more storage and memory.
They are questioning whether the companies tied to that demand can continue delivering growth fast enough to justify the enormous gains already seen in their stocks.
What investors should watch next
There are a few numbers that could become increasingly important for this sector:
1. Data center demand
AI infrastructure spending remains the biggest driver. If hyperscalers continue expanding aggressively, storage demand should remain supported.
2. Memory and storage pricing
Higher prices have been a major boost to industry earnings. Any meaningful slowdown could pressure margins and investor sentiment.
3. Margins
After such a strong run, investors will want to know whether today’s elevated margins can be maintained.
4. Capacity and new technology
Higher-capacity drives and improvements in storage technology could allow companies to handle more data without proportionally increasing manufacturing capacity.
5. Valuations
This may ultimately be the biggest issue.
A company can report excellent results and still see its stock fall if investors had already expected something even better.
The takeaway
Thursday’s selloff does not necessarily mean the AI storage boom is fading.
If anything, the underlying demand numbers remain impressive.
The bigger story is that the market has raised the bar.
Sandisk and Western Digital are operating in businesses benefiting from one of the strongest technology investment cycles in years. But after enormous stock-price gains, investors are no longer satisfied with strong earnings alone.
They want accelerating demand, expanding margins and forecasts that leave room for another upside surprise.
That is a much harder standard to meet.
And for the broader AI trade, this could become an important theme going forward:
The question may no longer be whether AI spending is growing. It may be whether the growth is strong enough to justify what investors are already paying for it.