{
  "slug": "backblaze-q4-2025-afr-by-age",
  "title": "Backblaze AFR by drive power-on age, Q4 2025",
  "kind": "dataset",
  "summary": "Annualized failure rate by drive power-on age, computed from Backblaze's raw daily Drive Stats files for Q4 2025 (October 1 to December 31, 2025) with the exposure counted per age bucket. Sample: hard drives of 3 TB or more with a power-on-hours value, 30,575,671 drive days and 926 failures (1.11% pooled AFR). The rate is 0.36% at 1 to under 2 years, 2.59% at 6 to under 7 and 7.08% at 7 to under 8, from 44 failures in 0.7% of drive days. Association only, one fleet and one quarter, with model mix that changes by age.",
  "license": "Derivative table computed from the Backblaze Drive Stats daily files for Q4 2025. Cite Backblaze if you use it. You are solely responsible for how you use it. Backblaze's dataset page allows sale of derivative works and forbids selling the Drive Stats data itself. This CSV is a 32-row aggregate, not the daily SMART archive, and that archive is not for sale.",
  "licenseUrl": "https://www.backblaze.com/cloud-storage/resources/hard-drive-test-data",
  "sourceUrl": "https://www.backblaze.com/cloud-storage/resources/hard-drive-test-data",
  "accessed": "2026-10-10",
  "rowCount": 32,
  "columns": [
    {
      "name": "size_class",
      "type": "string",
      "description": "All hard drives of 3 TB or more, or a nominal capacity class: up to 12 TB, 14 to 16 TB, 20 TB and above."
    },
    {
      "name": "age_years",
      "type": "string",
      "description": "Power-on age bucket in years, from smart_9_raw hours divided by 8766 on each drive day. The last bucket is 8 or more."
    },
    {
      "name": "drive_days",
      "type": "integer",
      "description": "Daily rows (drive days) of the class that fell in the bucket between 2025-10-01 and 2025-12-31. This is the exposure."
    },
    {
      "name": "share_of_class_drive_days_percent",
      "type": "number",
      "description": "The bucket's share of the class's drive days with an age, one decimal."
    },
    {
      "name": "failures",
      "type": "integer",
      "description": "Rows with failure = 1 in the bucket."
    },
    {
      "name": "afr_percent",
      "type": "number",
      "description": "failures / drive_days * 365 * 100, two decimals. Computed here."
    },
    {
      "name": "afr_low95",
      "type": "number",
      "description": "Lower bound of the exact two-sided 95% Poisson (Garwood) interval, in percent. Computed here."
    },
    {
      "name": "afr_high95",
      "type": "number",
      "description": "Upper bound of the same interval, in percent."
    }
  ],
  "downloadPath": "/data/datasets/backblaze-q4-2025-afr-by-age.csv",
  "chartPath": "/data/datasets/backblaze-q4-2025-afr-by-age.svg",
  "citations": [
    {
      "id": "bb-data",
      "title": "Backblaze Hard Drive Test Data, data_Q4_2025.zip (daily files, 92 CSVs)",
      "url": "https://f001.backblazeb2.com/file/Backblaze-Hard-Drive-Data/data_Q4_2025.zip",
      "accessed": "2026-10-10"
    },
    {
      "id": "bb-page",
      "title": "Hard Drive Reliability & Test Data",
      "url": "https://www.backblaze.com/cloud-storage/resources/hard-drive-test-data",
      "accessed": "2026-10-10"
    },
    {
      "id": "garwood-1936",
      "title": "Garwood, F. (1936). Fiducial limits for the Poisson distribution. Biometrika 28(3/4), 437-442",
      "url": "https://doi.org/10.1093/biomet/28.3-4.437",
      "accessed": "2026-10-10"
    }
  ]
}