{
  "slug": "nfs-write-verifier",
  "term": "NFS write verifier",
  "aliases": [
    "NFSv3 write verifier",
    "writeverf3"
  ],
  "definition": "An NFSv3 write verifier is a server cookie returned by WRITE and COMMIT that lets clients detect state changes that may have lost uncommitted writes.",
  "note": "The verifier distinguishes server states relevant to buffered-write recovery; it is not a data checksum, transaction identifier or cryptographic authentication token. When a returned verifier differs from the one associated with uncommitted buffers, the client retransmits those buffers and establishes stable completion again. Verifier comparison accompanies status, byte-count and stability checks; equality alone does not establish that a write was stable.",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "Detection requires retained client state and does not itself supply or repair lost data.",
      "citationIds": [
        "rfc1813"
      ]
    }
  ],
  "related": [
    "nfs-storage",
    "nfs-commit",
    "io-timeout"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "rfc1813",
      "title": "B. Callaghan, B. Pawlowski and P. Staubach. NFS Version 3 Protocol Specification. RFC 1813, June 1995, sections 3.3.7, 3.3.21 and 4.8.",
      "url": "https://www.rfc-editor.org/rfc/rfc1813.html",
      "accessed": "2026-10-12"
    },
    {
      "id": "hesela-stability",
      "title": "NFS stable writes: what COMMIT, flush and FUA actually promise",
      "url": "https://hesela.com/analyses/nfs-stable-writes-flush-fua/",
      "accessed": "2026-10-12"
    }
  ],
  "updated": "2026-10-12"
}