{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13",
  "slug": "completion-latency",
  "term": "Completion latency (fio)",
  "aliases": [
    "clat"
  ],
  "definition": "Completion latency in fio is the engine-dependent interval from submission of an I/O unit to observation of its completion.",
  "note": "For asynchronous I/O, observation includes fio reaping the completion; clat is not necessarily time spent only inside a storage device [fio]. Pool compatible clat means using their own sample counts; a zero-sample mean does not measure zero latency [fio-stat].",
  "related": [
    "submission-latency",
    "latency-storage",
    "queue-depth",
    "iops"
  ],
  "citations": [
    {
      "id": "fio",
      "title": "fio documentation: interpreting slat, clat and lat; engine-dependent timing boundaries.",
      "url": "https://fio.readthedocs.io/en/master/fio_doc.html",
      "accessed": "2026-10-13"
    },
    {
      "id": "fio-stat",
      "title": "fio 3.41 source: stat.c, add_ddir_lat_json and add_ddir_status_json; latency sample counts and directional runtime denominators.",
      "url": "https://github.com/axboe/fio/blob/fio-3.41/stat.c#L1410-L1600",
      "accessed": "2026-10-13"
    },
    {
      "id": "hesela-populations",
      "title": "Hesela: fio summaries, latency sample populations and runtime denominators; synthetic examples.",
      "url": "https://hesela.com/analyses/storage-latency-coordinated-omission/#fio-populations",
      "accessed": "2026-10-13"
    }
  ]
}