# TiKV IO causal ordering

<!-- auto-oncall-optimization-record
{
  "schemaVersion": "auto-oncall-optimization-record-v1",
  "optimizationId": "tikv-io-causal-ordering-2026-08-06",
  "problems": [
    {
      "problemId": "tikv-workload-induced-io-conflated-with-independent-storage-failure",
      "summary": "A TiKV storage scenario paragraph ordering workload volume against independent disk, engine, throttle, or write-stall evidence was tested on workload-driven, ambiguous, and device-driven cases. The baseline already preserved the same ordering and uncertainty, so the paragraph produced no material target improvement and was reverted.",
      "status": "ineffective",
      "issueKeys": ["TCID-12948", "APID-29259", "APID-29211", "APID-29298"],
      "sourceRefs": [
        "https://tidb.atlassian.net/browse/TCID-12948#problem:write-amplification-not-disk-throughput-limit",
        "https://tidb.atlassian.net/browse/APID-29259#problem:key-contention-versus-slow-storage-unresolved"
      ],
      "signalTextIncludesAny": [
        "workload induced io called independent storage failure",
        "disk symptom ranked without workload ordering",
        "tiny throttle value treated as primary cause"
      ],
      "observedThrough": "2026-08-06",
      "effectiveAt": null,
      "verifiedAt": "2026-08-06T13:52:00+08:00",
      "attemptedAction": "Add a tikv-storage-io paragraph that makes workload primary when scan or write volume explains the IO boundary and storage primary only when independent disk, engine, throttle, or stall evidence leads.",
      "evidenceUrl": null
    }
  ]
}
-->

- Owner: auto-oncall-services
- Implementation status: evaluated locally and reverted; not deployed
- Effective status: `ineffective`

## Verification

Single-variable A/B on two targets and two controls changed no causal status,
primary mechanism, uncertainty boundary, or action. The existing producer,
consumer, disk/engine-counterpart, and hotspot checks already did this work.

## Next action

Revisit only for a case where aligned workload and storage evidence reaches
the scenario but the existing contract still reverses their causal ordering.