Methodology

Backblaze publishes a daily snapshot of every hard drive in its data centers, one row per drive per day, including whether that drive failed that day. drives.fail ingests every quarterly release of that dataset (2013–present) into its own database and computes the same statistic Backblaze uses in its own quarterly reports.

Annualized Failure Rate (AFR)

For a given model and time period:

• Drive days — the total number of days across all drives of that model observed in the period.
• Drive years — drive days ÷ 365.
• Failures — the number of drives of that model that failed during the period.
• AFR — 100 × failures ÷ drive years.

Two versions of this are shown for every model: the current quarter (the most recently ingested reporting period) and lifetime (cumulative since 2013). One difference from Backblaze's own quarterly reports: their lifetime table only includes models still active in the current fleet. This site's lifetime numbers cover every model Backblaze has ever reported on, including ones long since retired -- nothing drops off just because it stopped shipping.

Data source

Every number on this site is derived from Backblaze's own published CSV exports, available at backblaze.com/cloud-storage/resources/hard-drive-test-data. drives.fail is an independent project, not affiliated with or endorsed by Backblaze.