{
  "slug": "track-skew",
  "term": "Track skew",
  "aliases": [
    "track skew factor"
  ],
  "definition": "Track skew is the sector-position offset between successive HDD tracks used to accommodate track-switch time during sequential access.",
  "note": "The platter keeps rotating while access switches tracks. Offsetting the next logical sector allows it to arrive after the switch instead of having already passed the head. This is a sector-layout offset, not the head's physical skew angle. [atropos-skew]\n\nTerminology can distinguish transitions: the ST3655 manual describes track skew between tracks in the same cylinder and cylinder skew across cylinders. Its actual factors vary by recording zone. [skew-manual]\n\nDo not infer that a field is adjustable from a successful command alone. The same manual says attempts to change either skew factor receive good status even though the initiator cannot directly change it. This is documented behavior of that drive family. [skew-manual]\n\nAtropos used track geometry for a research volume manager; its results are not a modern-device benchmark or a universal recommendation for filesystem layout. [atropos-skew]\n\nA skew count is not a duration. In Atropos's zoned-geometry discussion, track-switch time stays fixed while the number of sectors passing during that interval changes between zones. Comparing sector offsets without the local sectors-per-track and rotation period can therefore misrepresent switching cost. This is a distinction in the paper's model, not a measurement of a current drive. [atropos-skew]",
  "status": "unknown",
  "advantages": [],
  "limitations": [],
  "related": [
    "hdd",
    "zoned-bit-recording"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "atropos-skew",
      "title": "Schindler, Schlosser, Shao, Ailamaki and Ganger: Atropos, USENIX FAST 2004, sections 3.2, 3.3.1 and 5.1-5.3",
      "url": "https://www.usenix.org/legacy/publications/library/proceedings/fast04/tech/full_papers/schindler/schindler_html/",
      "accessed": "2026-10-24"
    },
    {
      "id": "skew-manual",
      "title": "Seagate: ST3655 Family SCSI Product Manual, Rev. A, 18 January 1994, section C.3, printed pp. 96-97",
      "url": "https://www.seagate.com/support/disc/manuals/scsi/3655npmb.pdf",
      "accessed": "2026-10-24"
    }
  ],
  "updated": "2026-10-24",
  "provenance": [
    "Historical implementation evidence and a research prototype; neither source establishes an invention date."
  ]
}