Seagate Vs. Western Digital: One Moved First on AI Storage Demand. The Other Is Playing It Safe.

Seagate Vs. Western Digital: One Moved First on AI Storage Demand. The Other Is Playing It Safe.

Alex Sirois

Mon, September 14, 2026 at 5:09 PM GMT+3 4 min read

Quick Read

• Seagate's 44TB HAMR drives already ship to 75% of top cloud customers, while Western Digital's competing drive won't reach hyperscalers until 2027.

• Seagate expanded gross margin to 52% from 37% YoY, but with shares up 325%, Western Digital's P/E of 17 draws value-focused investors.

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Seagate Technology (NASDAQ:STX) and Western Digital (NASDAQ:WDC) both closed fiscal 2026 with blockbuster quarters and guided fiscal Q1 2027 revenue to roughly $4.10 billion. Seagate is ramping HAMR-based Mozaic drives into hyperscale contracts today. Western Digital, now a pure-play HDD company after the Sandisk separation, is stretching ePMR further before its own HAMR product ships in 2027.

HAMR Ships Now for Seagate. Western Digital Squeezes ePMR Harder.

Seagate posted Q4 revenue of $3.63B, up 48.5% YoY, with non-GAAP EPS of $5.71 topping the $5.0932 consensus. Mozaic 4 drives, capable of up to 44 terabytes per drive, were shipping for revenue to 75% of the leading global cloud customers by March. CEO Dave Mosley told investors Seagate sees "durable long-term demand for mass capacity storage" anchored by its HAMR roadmap.

Western Digital's quarter showed revenue of $3.75B, up 43.8% YoY, EPS of $3.56, and gross margin of 54.4%. Growth is driven by 40TB ePMR. The 44TB Hammer drive ships in the first half of calendar year 2027. CEO Irving Tan framed this as disciplined execution.

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Business Driver

Seagate

Western Digital

Lead HDD Technology

Mozaic HAMR shipping

40TB ePMR + UltraSMR

Next Milestone

Mozaic 5, 50TB, late 2027

44TB Hammer, 1H 2027

Cloud Customer Traction

75% of top cloud customers on Mozaic

Cloud = 89% of Q4 revenue

First Mover Versus Fast Follower

Seagate prioritizes areal density rather than increasing unit volumes, with nearline capacity almost fully allocated through calendar 2027. Western Digital is playing the patient hand. WD's exabyte shipments grew 22% year over year in Q4, but cost-per-terabyte fell only approximately 8% year over year. Seagate's HAMR economics are pulling costs faster.

Lens

STX

WDC

Core Bet

First mover on HAMR

Extend ePMR runway

Key Vulnerability

Hyperscaler concentration, BIS settlement

Late to HAMR volume

Forward P/E

Next Test: HAMR Qualification Speed

Watch whether Seagate can push 70% of nearline exabytes onto HAMR by fiscal 2027 without yield issues. For Western Digital, 44TB Hammer qualification with hyperscalers in early 2027 is critical. Also monitor pricing on LTAs extending to calendar years 2029, 2030 and 2031, where WD said commercial constructs are still being negotiated.

Why I Lean Toward Seagate After This Quarter

Seagate's HAMR head start is real, gross margin expanded to 52.3% from 37.4% YoY, and free cash flow hit a record $3.1B for the year. Shares are up 325.27% over the past year, so valuation is not cheap. Western Digital trades at a P/E of 17 with a cleaner balance sheet, a profile often screened by value-oriented investors. Both names face risk if HAMR qualification slips or hyperscaler capex cools. Storage sits alongside power, cooling, and networking on the list of non-chipmaker AI beneficiaries we pulled together in a free report on seven of them.

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