What the latest data reveals about hard drive reliability
What really counts as a hard drive failure? That’s the question at the center of Backblaze’s Q3 2025 Drive Stats report, which tracks the performance of 328,348 hard drives across its global data centers. The latest findings build on more than a decade of data that has made Backblaze one of the most transparent sources on drive reliability for IT teams, researchers, and data professionals.
Backblaze hard drive failure rates for Q3 2025
“After more than ten years and billions of drive days, we’ve built one of the largest collections of drive reliability data in the world,” said Gleb Budman, CEO of Backblaze. “This quarter, we’re going deeper, and showing exactly how we spot drive failures and turning that insight into something anyone can use.”
The quarterly failure rate ticked up slightly, from 1.36% in Q2 to 1.55% in Q3, closely matching the 2024 annualized failure rate (AFR) of 1.57%. Four models had zero recorded failures this quarter: the Seagate HMS5C4040BLE640 (4TB), Seagate ST8000NM000A (8TB), Toshiba MG09ACA16TE (16TB), and the newly added Toshiba MG11ACA24TE (24TB).
High-capacity drives (20TB and up) continued to grow in use, adding nearly 8,000 units and now making up 21% of Backblaze’s active drive pool. The lifetime AFR held steady at 1.31%, consistent with the past two quarters.
This quarter’s report takes a closer look at how Backblaze determines when a drive has actually failed. The company uses SMART data, internal monitoring tools, and automated tracking systems to tell true mechanical failures apart from temporary removals. A drive is marked as failed if it is flagged in work tracking systems or does not return to service by the end of the quarter.
One outlier stood out: the Toshiba MG08ACA16TEY (16TB), which posted a 16.95% AFR. The spike, Backblaze explained, came from an infrastructure upgrade that temporarily pulled several drives from operation, not from actual hardware failures. The company expects those figures to level out in future reports.