{
  "slug": "storage-availability",
  "term": "Storage availability",
  "aliases": [
    "data availability"
  ],
  "definition": "Storage availability is the ability of a storage service to provide the required data access to a specified client under stated operating conditions.",
  "note": "A preserved copy does not ensure an operational path from every host. Specify the client, operation and tolerated failures before making an availability claim. [snia-durability-availability]\n\nAvailability percentages need a measurement contract. The cited object-storage metric averages five-minute eligible-error ratios, rather than simply dividing all errors by all requests; its idle-interval convention also matters. [aws-s3-sla]\n\nThe companion analysis gives two synthetic traffic patterns with the same total requests and errors but different interval-weighted results. Neither result establishes outage duration, end-to-end application success or a durability probability.\n\nA status-based metric does not by itself establish completion before an application's deadline; evaluate the latency distribution separately. [dean-barroso-tail-2013]",
  "related": [
    "data-durability",
    "failure-domain",
    "recovery-time-objective",
    "io-timeout",
    "fail-slow",
    "tail-latency"
  ],
  "status": "unknown",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-22",
  "citations": [
    {
      "id": "snia-durability-availability",
      "title": "SNIA: NVM PM Remote Access for High Availability, May 2019, section 4.1, pp. 13-15 (non-normative whitepaper)",
      "url": "https://www.snia.org/sites/default/files/2024-12/SNIA-NVM-PM-Remote-Access-for-High-Availability-WP.pdf",
      "accessed": "2026-10-22"
    },
    {
      "id": "aws-s3-sla",
      "title": "Amazon S3 Service Level Agreement, updated 28 November 2023, Definitions",
      "url": "https://aws.amazon.com/s3/sla/",
      "accessed": "2026-10-22"
    },
    {
      "id": "dean-barroso-tail-2013",
      "title": "Dean and Barroso: The Tail at Scale, CACM 56(2), 2013, pp. 74-80, DOI 10.1145/2408776.2408794",
      "url": "https://research.google/pubs/the-tail-at-scale/",
      "accessed": "2026-10-22"
    }
  ],
  "provenance": [
    "The synthetic comparison is arithmetic, not service telemetry or a credit-eligibility assessment. No aggregation across different request types is inferred."
  ]
}