{
  "slug": "sequential-io",
  "term": "Sequential I/O",
  "aliases": [
    "Sequential input/output",
    "Sequential access pattern"
  ],
  "definition": "Sequential I/O is an access pattern in which successive requests in a stream address adjacent address ranges in order.",
  "note": "Address order: Small requests can be sequential; request size is a separate workload setting [snia][fio]. In a NAND SSD, host logical adjacency does not establish adjacent physical placement, because an FTL maps logical addresses to physical locations [agrawal].\n\nBenchmark setup: fio selects sequential reads or writes with rw=read or rw=write; blocksize and iodepth configure different dimensions. With multiple outstanding requests, completion order need not match submission order [fio].",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "random-io",
    "io-request-size",
    "queue-depth",
    "iops",
    "throughput-storage",
    "ssd",
    "hdd",
    "posix-fadv-sequential"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "snia",
      "title": "SNIA Dictionary, 28 April 2026: random I/O and sequential I/O, pp. 244-245 and 270.",
      "url": "https://www.snia.org/sites/default/files/dictionary/SNIADictionary.pdf",
      "accessed": "2026-10-24"
    },
    {
      "id": "fio",
      "title": "fio documentation: rw, blocksize, random_distribution, iodepth and serialize_overlap.",
      "url": "https://fio.readthedocs.io/en/latest/fio_doc.html",
      "accessed": "2026-10-24"
    },
    {
      "id": "agrawal",
      "title": "Agrawal et al. Design Tradeoffs for SSD Performance. USENIX ATC 2008, section 3.1.",
      "url": "https://www.usenix.org/legacy/events/usenix08/tech/full_papers/agrawal/agrawal.pdf",
      "accessed": "2026-10-24"
    }
  ],
  "provenance": [
    "The definitions are original paraphrases, not reproductions of SNIA Dictionary entries.",
    "The fio online manual was reviewed on 24 October 2026; option semantics describe a workload generator, not measured device performance."
  ],
  "updated": "2026-10-24"
}