{
  "slug": "differential-observability",
  "term": "Differential observability",
  "aliases": [],
  "definition": "Differential observability is a difference between entities' observations of the same system's health.",
  "note": "The gray-failure case is asymmetric: the application observes trouble and the internal observer does not; a detector noticing a problem before an application is affected is a different case. [huang-hotos17]",
  "related": [
    "gray-failure",
    "fail-slow"
  ],
  "citations": [
    {
      "id": "huang-hotos17",
      "title": "Huang et al., Gray Failure: The Achilles' Heel of Cloud-Scale Systems, HotOS 2017, section 3; DOI 10.1145/3102980.3103005.",
      "url": "https://www.microsoft.com/en-us/research/wp-content/uploads/2017/06/paper-1.pdf",
      "accessed": "2026-10-13"
    },
    {
      "id": "hesela-observers",
      "title": "Hesela: Fail-slow NVMe SSDs: what SMART and heartbeats miss",
      "url": "https://hesela.com/analyses/nvme-fail-slow-unseen-by-smart/",
      "accessed": "2026-10-13"
    }
  ],
  "status": "unknown",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13"
}