SanDisk and Western Digital shares surged 6% on Friday as AI-driven demand for storage chips and hard drives propels both stocks to record highs, though traders remain divided on whether the rally reflects a multi-year boom or late-stage excess.

What happened: SanDisk stock rose 6% to near $1,989 and Western Digital climbed 6% to $561 on Friday. 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 AI infrastructure demand for memory chips and hard-disk drives.

Why it matters: SanDisk's Q3 FY2026 results delivered revenue of $5.95 billion（約9500億円） (up 251% year over year) and data-center segment revenue jumped 645% year over year to $1.47 billion（約2400億円）, while Western Digital reported revenue of $3.34 billion（約5300億円） (up 46% year over year) and non-GAAP gross margin cleared 50% for the first time in recent memory. Both companies have guided for strong Q4 results, suggesting sustained momentum from AI workloads that create persistent data storage needs.

What to watch: SanDisk has locked in approximately $42 billion（約6.7兆円） in multi-year supply agreements, and Susquehanna carries a $2,000 price target on SNDK stock, the highest on the Street. However, insider selling has surfaced—a director offloaded 579 shares near $1,503 in early May—and bearish sentiment on social media suggests the move may be overextended. Incoming NAND and hard-disk drive pricing data will be the key signal for whether the rally is sustainable.