SanDisk and Western Digital jump 6% as traders debate whether soaring AI storage demand signals a multi-year boom or a stretched bubble.

What happened: SanDisk shares rose 6% to near $1,989 on Friday, while Western Digital climbed 6% to $561. SanDisk has gained 724% year to date and 4,638% over the past 12 months; Western Digital is up 224% YTD and 902% over the past year, driven by surging demand for memory and hard-disk drive capacity from AI data centers.

Why it matters: The run reflects genuine operational momentum. SanDisk reported Q3 FY2026 revenue of $5.95 billion（約9500億円）, up 251% year over year, with data-center segment revenue jumping 645% YoY to $1.47 billion（約2400億円）. Western Digital's non-GAAP gross margin cleared 50% for the first time in recent memory as AI workloads tightened hard-disk drive supply. However, the market is divided on sustainability—bulls point to SanDisk's approximately $42 billion（約6.7兆円） in locked multi-year supply agreements, while bears cite stretched valuations and insider selling, including a director offloading 579 shares near $1,503 in early May.

What to watch: SanDisk has guided Q4 FY2026 revenue to $7.75 billion（約1.2兆円） to $8.25 billion（約1.3兆円） and non-GAAP EPS of $30 to $33. Western Digital guided Q4 FY2026 revenue to roughly $3.65 billion（約5800億円） and non-GAAP EPS of $3.25, plus or minus $0.15. Incoming NAND and hard-disk drive pricing data will be the dominant signal for whether the rally holds or expectations reset in the next earnings cycle.