{
  "aliases": [
    "dm-snapshot exception store"
  ],
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-22",
  "slug": "snapshot-exception-store",
  "term": "Snapshot exception store",
  "definition": "A snapshot exception store records changed-chunk mappings used to reconstruct a classic device-mapper snapshot.",
  "note": "The snapshot reads unchanged chunks from its origin and changed chunks from its copy-on-write device. The exception metadata identifies that correspondence. The COW device is therefore not a standalone full-volume image. [dm-snapshot]\n\nPersistent stores retain the metadata across reboots; transient stores do not. [dm-snapshot]",
  "related": [
    "snapshot",
    "snapshot-merge",
    "copy-on-write",
    "lvm",
    "volume-manager"
  ],
  "citations": [
    {
      "id": "dm-snapshot",
      "title": "Linux device-mapper: snapshot targets and merge completion",
      "url": "https://docs.kernel.org/admin-guide/device-mapper/snapshot.html",
      "accessed": "2026-10-22"
    }
  ],
  "provenance": [
    "Scope: classic Linux dm-snapshot, not dm-thin, filesystem snapshots or exception handling in a programming language."
  ]
}