{
  "slug": "automated-storage-tiering",
  "term": "Automated storage tiering",
  "aliases": [
    "auto-tiering"
  ],
  "definition": "Automated storage tiering relocates data among storage classes according to a policy without requiring a person to perform each move.",
  "note": "Scope: Tiers can differ in performance, capacity or cost. Their existence does not imply automatic movement; automation adds policy-controlled relocation within or across systems, including a cloud tier. [snia-tiers] [snia-auto]\n\nPolicy and placement are different states. In the cited volume-tiering implementation, changing auto to none does not itself recall blocks already in the capacity tier. Separate retrieval controls affect their return. Check actual placement after a policy change. [fabricpool-policy]\n\nRetrieval: From ONTAP 9.8, cloud-retrieval-policy can override tiering defaults. Under default retrieval, auto brings cold data back on random reads but not sequential reads; on-read brings it back for either pattern, while never leaves read blocks in the cloud. Reading only filenames, timestamps or ownership metadata does not heat the underlying data blocks. [fabricpool-policy] [fabricpool-recovery]\n\nCompletion: Using none plus promote requests proactive retrieval of all tiered volume data. Using snapshot-only plus promote targets tiered active-filesystem data, not blocks used only by snapshots. Check promotion status with volume object-store tiering show; accepting a policy change is not proof that promotion has finished. [fabricpool-promote]\n\nCache safety cannot be reduced to a move-versus-copy distinction. A dirty write-back block can be newer than its stale origin copy; losing that cache can lose updates. The cited cache also describes promotion and demotion as migration. [dm-cache-612]\n\nA capacity tier is not an independent backup merely because it is remote. In the cited architecture, required metadata stays on the performance tier, so the capacity-tier blocks alone cannot reconstruct the system after that metadata is lost. [fabricpool-recovery]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "Automatic placement does not establish immediate migration or a guarantee that every read promotes data.",
      "citationIds": [
        "fabricpool-policy"
      ]
    }
  ],
  "related": [
    "hot-warm-cold",
    "hybrid-flash-array",
    "write-back-cache",
    "object-storage"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "snia-auto",
      "title": "SNIA Dictionary: automated storage tiering, policy-controlled movement within and across systems.",
      "url": "https://www.snia.org/education/online-dictionary/term/automated-storage-tiering",
      "accessed": "2026-10-31"
    },
    {
      "id": "snia-tiers",
      "title": "SNIA Dictionary: tiered storage, distinct classes and optional dynamic movement.",
      "url": "https://www.snia.org/education/online-dictionary/term/tiered-storage",
      "accessed": "2026-10-31"
    },
    {
      "id": "snia-alias",
      "title": "SNIA Dictionary: auto-tiering synonym.",
      "url": "https://www.snia.org/education/online-dictionary/term/auto-tiering",
      "accessed": "2026-10-31"
    },
    {
      "id": "fabricpool-policy",
      "title": "NetApp ONTAP: FabricPool volume tiering policies, policy changes and cloud retrieval controls.",
      "url": "https://docs.netapp.com/us-en/ontap/fabricpool/tiering-policies-concept.html",
      "accessed": "2026-10-31"
    },
    {
      "id": "dm-cache-612",
      "title": "Linux 6.12: dm-cache glossary and cache operating modes, origin-copy and writeback semantics.",
      "url": "https://www.kernel.org/doc/html/v6.12/admin-guide/device-mapper/cache.html",
      "accessed": "2026-10-31"
    },
    {
      "id": "fabricpool-recovery",
      "title": "NetApp: Oracle database FabricPool tiering overview, Architecture, Data and metadata, and Backups.",
      "url": "https://docs.netapp.com/us-en/ontap-apps-dbs/oracle/oracle-tiering-overview.html",
      "accessed": "2026-10-31"
    },
    {
      "id": "fabricpool-promote",
      "title": "NetApp ONTAP: Promote data to the performance tier, ONTAP 9.8 and later; requested scope and promotion-status check.",
      "url": "https://docs.netapp.com/us-en/ontap/fabricpool/promote-data-performance-tier-task.html",
      "accessed": "2026-10-31"
    }
  ],
  "updated": "2026-10-31",
  "provenance": [
    "SNIA supplies the terminology and auto-tiering alias; the broader storage tiering alias remains attached to hot-warm-cold. [snia-auto] [snia-tiers] [snia-alias]",
    "FabricPool supplies the policy-change, retrieval and metadata examples; these are not universal rules for every tiering system. [fabricpool-policy] [fabricpool-recovery]",
    "Linux 6.12 supplies a counterexample to treating every cache as a disposable current copy. [dm-cache-612]",
    "Documentation synthesis, not a device experiment, measured speedup or independent recovery test.",
    "The ONTAP promotion procedure documents requested data scope and a separate status check; this is not a completed recall or a tier-removal procedure tested by Hesela. [fabricpool-promote]"
  ]
}