{
  "slug": "ufs-writebooster",
  "term": "UFS WriteBooster",
  "aliases": [
    "WriteBooster"
  ],
  "definition": "UFS WriteBooster is a host-controlled feature that uses a finite SLC-mode flash buffer to accelerate writes.",
  "note": "KIOXIA describes incoming writes using the user area when the buffer fills, and host-authorized migration there during idle or hibernate periods. This extra movement can increase write amplification. The buffer operates NAND in one-bit mode; it is not a volatile DRAM cache. [writebooster-brief]\n\nLinux v6.12 separates buffer-flush permission from status: wb_flush_status distinguishes idle, ongoing, prematurely stopped, successful and failed operations. Enabling flushing does not establish successful completion. [ufs-abi-612]\n\nWriteBooster buffer migration is not the Linux block layer's volatile-cache preflush or per-write FUA completion contract. Treat their different uses of \"flush\" separately. This is a comparison of documented interfaces, not a device power-loss test. [writebooster-brief] [writeback-612]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "A burst write rate does not establish sustained throughput after buffer exhaustion.",
      "citationIds": [
        "writebooster-brief"
      ]
    }
  ],
  "related": [
    "ufs",
    "slc-cache",
    "write-amplification",
    "ftl",
    "cache-flush",
    "force-unit-access"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-04",
  "citations": [
    {
      "id": "writebooster-brief",
      "title": "KIOXIA: Understanding the WriteBooster Feature, January 2023, Rev. 2.0, pages 1-3",
      "url": "https://americas.kioxia.com/content/dam/kioxia/shared/business/memory/mlc-nand/asset/productbrief/KIOXIA_WriteBooster_Feature_Tech_Brief.pdf",
      "accessed": "2026-11-04"
    },
    {
      "id": "ufs-abi-612",
      "title": "Linux v6.12: UFS sysfs ABI, WriteBooster controls, attributes and effective capabilities",
      "url": "https://raw.githubusercontent.com/torvalds/linux/v6.12/Documentation/ABI/testing/sysfs-driver-ufs",
      "accessed": "2026-11-04"
    },
    {
      "id": "writeback-612",
      "title": "Linux v6.12: Explicit volatile write back cache control, REQ_PREFLUSH and REQ_FUA",
      "url": "https://raw.githubusercontent.com/torvalds/linux/v6.12/Documentation/block/writeback_cache_control.rst",
      "accessed": "2026-11-04"
    },
    {
      "id": "analysis",
      "title": "Hesela: eMMC, UFS and RPMB: interface, boot and security boundaries",
      "url": "https://hesela.com/analyses/emmc-ufs-rpmb-boundaries/",
      "accessed": "2026-10-17"
    }
  ],
  "provenance": [
    "Source review of a dated vendor brief and Linux v6.12, not a JEDEC conformance review, measured throughput result or universal device guarantee."
  ]
}