{
  "slug": "s3-durability-eleven-nines-derivation",
  "title": "Eleven nines: what a durability model does not prove",
  "kind": "dataset",
  "summary": "Historical source figures and reproducible fixed-window arithmetic: distinguish Poisson event counts from distinct-shard binomial probabilities, with explicit storage-class scope.",
  "license": "No standalone reuse license has been verified for this mixed-source derived CSV. It combines attributed source figures and labeled arithmetic; it is not an observed loss dataset or a copy of the papers. The sources retain their own rights.",
  "licenseUrl": "https://hesela.dev/datasets/s3-durability-eleven-nines-derivation/#rights-and-reuse",
  "sourceUrl": "https://www.backblaze.com/blog/cloud-storage-durability/",
  "accessed": "2026-10-15",
  "rowCount": 21,
  "columns": [
    {
      "name": "measure",
      "type": "string",
      "description": "The quantity as the source names it, or our derived quantity."
    },
    {
      "name": "value_low",
      "type": "number",
      "description": "Retained legacy range column; empty for this point-value extract."
    },
    {
      "name": "value_high",
      "type": "number",
      "description": "Point value, not an upper uncertainty bound; see scope and note."
    },
    {
      "name": "unit",
      "type": "string",
      "description": "Unit of the value."
    },
    {
      "name": "scope",
      "type": "string",
      "description": "Population and context the value applies to; 'Derived by us' marks our arithmetic."
    },
    {
      "name": "note",
      "type": "string",
      "description": "What the value is not, or the source wording behind it."
    },
    {
      "name": "citation_id",
      "type": "string",
      "description": "Id of the opened source in the citations list; several ids are separated by semicolons."
    }
  ],
  "downloadPath": "/data/datasets/s3-durability-eleven-nines-derivation.csv",
  "humanPage": "https://hesela.com/analyses/s3-durability-eleven-nines-derivation/",
  "limits": [
    "All window calculations assume independent, constant-rate shard failures and independent fixed periods. They do not model overlapping repairs, losses straddling period boundaries, latent corruption, shared dependencies or operational deletion. The fractional annual exponent is a historical approximation, not an event-driven repair simulation. Extra decimal digits reduce rounding error but do not reduce model uncertainty. No empirical confidence interval, provider ranking or guarantee follows.",
    "The 2018 Backblaze inputs are historical, not current provider measurements.",
    "The source extract has 21 rows; the separate model CSV has four deterministic parameter scenarios. Neither count is an empirical sample size.",
    "An expected loss count is not a guaranteed waiting time. Probability of any loss needs assumptions about dependence.",
    "The AWS storage-class source excludes One Zone classes from the three-zone claim."
  ],
  "citations": [
    {
      "id": "aws-s3-faq",
      "title": "Amazon S3 FAQs, Durability and Data Protection (AWS, vendor document)",
      "url": "https://aws.amazon.com/s3/faqs/",
      "accessed": "2026-10-15"
    },
    {
      "id": "aws-s3-userguide",
      "title": "AWS S3 User Guide: storage classes, durability and Availability Zone scope",
      "url": "https://docs.aws.amazon.com/AmazonS3/latest/userguide/storage-class-intro.html",
      "accessed": "2026-10-15"
    },
    {
      "id": "backblaze-2018",
      "title": "Backblaze Durability Calculates at 99.999999999% And Why It Doesn't Matter, Brian Wilson, Backblaze blog, 17 July 2018 (vendor derivation)",
      "url": "https://www.backblaze.com/blog/cloud-storage-durability/",
      "accessed": "2026-10-15"
    },
    {
      "id": "greenan-hotstorage10-pdf",
      "title": "Mean time to meaningless: MTTDL, Markov models, and storage system reliability, Greenan, Plank, and Wylie, USENIX HotStorage 2010 (USENIX PDF, independent academic source)",
      "url": "https://www.usenix.org/legacy/event/hotstorage10/tech/full_papers/Greenan.pdf",
      "accessed": "2026-10-15"
    },
    {
      "id": "backblaze-notebook",
      "title": "Backblaze erasure-coding durability notebook, pinned revision 37f758d",
      "url": "https://github.com/Backblaze/erasure-coding-durability/blob/37f758d64240cfb42a6d6fd41ff4ca16b8499bb3/calculation.ipynb",
      "accessed": "2026-10-15"
    }
  ],
  "updated": "2026-10-15",
  "rightsStatus": "not-verified",
  "rightsScope": "derived-csv",
  "rightsReviewed": "2026-10-15",
  "rightsEvidence": [
    {
      "title": "Amazon S3 FAQs, Durability and Data Protection (AWS, vendor document)",
      "url": "https://aws.amazon.com/s3/faqs/",
      "accessed": "2026-10-15",
      "note": "Reviewed for factual provenance; this source is not a verified standalone reuse license for Hesela's mixed-source CSV."
    },
    {
      "title": "AWS S3 User Guide: storage classes, durability and Availability Zone scope",
      "url": "https://docs.aws.amazon.com/AmazonS3/latest/userguide/storage-class-intro.html",
      "accessed": "2026-10-15",
      "note": "Reviewed for factual provenance; this source is not a verified standalone reuse license for Hesela's mixed-source CSV."
    },
    {
      "title": "Backblaze Durability Calculates at 99.999999999% And Why It Doesn't Matter, Brian Wilson, Backblaze blog, 17 July 2018 (vendor derivation)",
      "url": "https://www.backblaze.com/blog/cloud-storage-durability/",
      "accessed": "2026-10-15",
      "note": "Reviewed for factual provenance; this source is not a verified standalone reuse license for Hesela's mixed-source CSV."
    },
    {
      "title": "Mean time to meaningless: MTTDL, Markov models, and storage system reliability, Greenan, Plank, and Wylie, USENIX HotStorage 2010 (USENIX PDF, independent academic source)",
      "url": "https://www.usenix.org/legacy/event/hotstorage10/tech/full_papers/Greenan.pdf",
      "accessed": "2026-10-15",
      "note": "Reviewed for factual provenance; this source is not a verified standalone reuse license for Hesela's mixed-source CSV."
    },
    {
      "title": "Backblaze erasure-coding durability notebook, pinned revision 37f758d",
      "url": "https://github.com/Backblaze/erasure-coding-durability/blob/37f758d64240cfb42a6d6fd41ff4ca16b8499bb3/calculation.ipynb",
      "accessed": "2026-10-15",
      "note": "Reviewed for factual provenance; this source is not a verified standalone reuse license for Hesela's mixed-source CSV."
    }
  ],
  "reproduction": {
    "code": "/research/durability-model.py",
    "json": "/research/durability-model.json",
    "csv": "/research/durability-model.csv",
    "python": "3.12 or newer; standard library only",
    "command": "python3 durability-model.py --output-dir results"
  }
}