{
  "slug": "data-reduction-ratio",
  "term": "Data-reduction ratio",
  "aliases": [
    "DRR"
  ],
  "definition": "A data-reduction ratio compares the logical data represented with its corresponding stored footprint under a stated accounting convention.",
  "note": "Calculation: Divide logical bytes by corresponding stored bytes using the same data population, time and units. A 2:1 ratio means 50% savings against the logical baseline. A zero-footprint sample provides no finite ratio for planning.\n\nScope: Reports differ in whether they count retained copies, metadata and allocation avoidance. Unwritten thin address space is not evidence of compressed data; identify what each counter includes. [ontap-capacity]\n\nAggregation: For non-overlapping populations with matching accounting, sum logical and stored bytes separately. Two hypothetical 100 TB logical populations occupying 100 TB and 25 TB give 200 / 125 = 1.6:1, not the mean 2.5:1. Shared deduplicated blocks need a pool total or an allocation that counts each block once. This is arithmetic, not an array measurement.\n\nPopulation: A ratio for reducible data only excludes the unreducible portion. Do not apply it to the whole workload without accounting for that omitted data. [powerstore-reduction]\n\nIncoming mix: Let f be the fraction of incoming logical bytes reduced at ratio r, with the rest costing 1:1. For additive footprints, physical bytes per logical byte are (1 - f) + f / r. At f = 0.5 and r = 4, the ratio is 1 / 0.625 = 1.6:1. This hypothetical model fixes old data and overhead; it excludes shared blocks, new metadata, retained-version growth and competing writers. It is not a product counter formula or a capacity guarantee.",
  "status": "unknown",
  "advantages": [],
  "limitations": [],
  "related": [
    "deduplication",
    "transparent-compression",
    "usable-capacity",
    "effective-capacity",
    "thin-provisioning",
    "all-flash-array",
    "duplication-frequency-histogram"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "ontap-capacity",
      "title": "NetApp ONTAP: capacity reporting and measurements",
      "url": "https://docs.netapp.com/us-en/ontap/concepts/capacity-measurements.html",
      "accessed": "2026-10-22"
    },
    {
      "id": "powerstore-reduction",
      "title": "Dell PowerStore Monitoring: overall and reducible data-reduction ratios",
      "url": "https://www.dell.com/support/manuals/en-us/powerstore-9000/pwrstr-monitoring/data-reduction?guid=guid-db85dda3-fe0d-40f1-bd9a-703696fda302&lang=en-us",
      "accessed": "2026-10-23"
    }
  ],
  "updated": "2026-10-23",
  "provenance": [
    "Terminology follows the cited accounting convention; no storage-array measurement or capacity guarantee is implied.",
    "NetApp documents that ONTAP 9.13.1 and later exclude snapshots and thin provisioning from its data-reduction ratio; earlier displays differ. [ontap-capacity]"
  ]
}