{
  "slug": "free-space-fragmentation",
  "term": "Free-space fragmentation",
  "aliases": [
    "free space fragmentation"
  ],
  "definition": "Free-space fragmentation is the division of a filesystem's available allocation space into separated contiguous runs.",
  "note": "The same number of free blocks can have different run sizes and locations. This constrains later allocation, but free space itself is not read in a scan of allocated file contents. Geriatrix targets both allocated-file and free-space layout.",
  "related": [
    "filesystem-aging",
    "dynamic-layout-score",
    "ssd-preconditioning"
  ],
  "limitations": [
    "An occupancy percentage is not a free-extent distribution.",
    "Logical free runs do not reveal the physical NAND layout behind an SSD's mapping layer."
  ],
  "citations": [
    {
      "id": "geriatrix",
      "title": "Kadekodi, Nagarajan, Ganger and Gibson. Geriatrix: Aging what you see and what you don't see. USENIX ATC 2018, pp. 691-704, sections 4-6.",
      "url": "https://www.usenix.org/system/files/conference/atc18/atc18-kadekodi.pdf",
      "accessed": "2026-10-14"
    },
    {
      "id": "conway19",
      "title": "Conway et al. Filesystem Aging: It's more Usage than Fullness. HotStorage 2019, sections 3-4 and Figure 3.",
      "url": "https://www.usenix.org/system/files/hotstorage19-paper-conway.pdf",
      "accessed": "2026-10-14"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-14"
}