{
  "schemaVersion": 1,
  "slug": "latency-arrival-cohorts",
  "kind": "dataset",
  "title": "Storage latency: synthetic arrival cohorts",
  "summary": "390 synthetic request records compare independent and completion-driven arrivals during one pause; downloadable timestamps reproduce the p99 calculation.",
  "published": "2026-10-12",
  "updated": "2026-10-12",
  "evidenceType": "deterministic-synthetic-example",
  "generatedAt": "2026-10-12T08:21:46.163Z",
  "runtime": {
    "node": "v24.21.0"
  },
  "method": "One FIFO server; 2000 ms half-open arrival window; 10 ms open interval; 1 ms normal service; first service has a 100 ms added pause. Closed loop: one client with 9 ms think time after completion. All cohort requests drain; nearest-rank empirical quantiles.",
  "limits": [
    "Not hardware data, not a fio run, not a paper reproduction, no device ranking or population inference. No random sampling, timeout, drop, retry, parallelism or cache. No confidence interval is applicable to these deterministic inputs.",
    "The open and closed cohorts have unequal loads and sizes. Do not pool them as one benchmark or infer a speedup.",
    "Each request is one row. Request indices restart for each mode; (mode, index) is the unique key."
  ],
  "humanPage": "https://hesela.com/analyses/storage-latency-coordinated-omission/",
  "sourceUrl": "https://hesela.com/analyses/storage-latency-coordinated-omission/",
  "downloadPath": "/data/datasets/latency-arrival-cohorts.csv",
  "codePath": "/research/latency-measurement.mjs",
  "testPath": "/research/latency-measurement.test.mjs",
  "generatorPath": "/research/build-latency-measurement.mjs",
  "recordsPath": "/research/latency-measurement.json",
  "license": "CC0-1.0 for Hesela's original synthetic records and calculation code; cited publications retain their own rights.",
  "licenseUrl": "https://creativecommons.org/publicdomain/zero/1.0/",
  "columns": [
    {
      "name": "mode",
      "type": "string",
      "description": "Separate synthetic scenario: open or closed; not a device label."
    },
    {
      "name": "index",
      "type": "integer",
      "description": "Zero-based request number within its scenario."
    },
    {
      "name": "arrivalMs",
      "type": "integer",
      "description": "Arrival and submission time in ms, inside [0, 2000)."
    },
    {
      "name": "startMs",
      "type": "integer",
      "description": "FIFO service start in ms; may follow arrival because of queueing."
    },
    {
      "name": "completedMs",
      "type": "integer",
      "description": "Completion time in ms; all admitted requests are drained."
    },
    {
      "name": "queueMs",
      "type": "integer",
      "description": "startMs minus arrivalMs, in ms."
    },
    {
      "name": "responseMs",
      "type": "integer",
      "description": "completedMs minus arrivalMs, in ms; not device service time."
    }
  ],
  "rowCount": 390,
  "scenarios": [
    {
      "mode": "open",
      "parameters": {
        "durationMs": 2000,
        "intervalMs": 10,
        "serviceMs": 1,
        "pauseMs": 100
      },
      "summary": {
        "requests": 200,
        "completedWithinWindow": 200,
        "completedAfterWindow": 0,
        "offeredRequestsPerSecond": 100,
        "meanMs": 4.03,
        "p50Ms": 1,
        "p99Ms": 83,
        "maxMs": 101,
        "above10Ms": 11,
        "finalCompletionMs": 1991
      }
    },
    {
      "mode": "closed",
      "parameters": {
        "durationMs": 2000,
        "intervalMs": 10,
        "serviceMs": 1,
        "pauseMs": 100
      },
      "summary": {
        "requests": 190,
        "completedWithinWindow": 190,
        "completedAfterWindow": 0,
        "offeredRequestsPerSecond": 95,
        "meanMs": 1.5263157894736843,
        "p50Ms": 1,
        "p99Ms": 1,
        "maxMs": 101,
        "above10Ms": 1,
        "finalCompletionMs": 1991
      }
    }
  ],
  "artifacts": {
    "modelSha256": "ca68c392f2789016c468c5ecadcd46a75fcb16056311c20b2b219bee1488e019",
    "testsSha256": "76cb444444d357ee2882e8acd317a567b5d6df9b511261340fa15c94f91220bb",
    "csvSha256": "c81177199867928588c1f577720916e560f2a907a1321856fc5f58844a9451b5",
    "generatorSha256": "fa48e3c3ef6eeb0c3fa34c246e8e91a7e7cc854dff07bb5c378ecd5190f87b20",
    "recordsSha256": "74eaefbfe36a693b62c25e4236bf8353dde167e245f1b0b02d735559e7dc44df"
  },
  "citations": [
    {
      "id": "schroeder",
      "title": "Schroeder, Wierman and Harchol-Balter. Open Versus Closed: A Cautionary Tale. USENIX NSDI 2006. Workload-model context, not the source of these synthetic records.",
      "url": "https://www.usenix.org/legacy/events/nsdi06/tech/full_papers/schroeder/schroeder_html/index.html",
      "accessed": "2026-10-12"
    },
    {
      "id": "hesela",
      "title": "Hesela: Storage latency: when the benchmark stops asking",
      "url": "https://hesela.com/analyses/storage-latency-coordinated-omission/",
      "accessed": "2026-10-12"
    }
  ]
}