{
  "slug": "physical-sector",
  "term": "Physical sector",
  "aliases": [
    "physical block (storage)"
  ],
  "definition": "A physical sector is the device-level data unit whose reported size describes physical read/write granularity rather than logical addressing.",
  "note": "Treat the reported value as information at a particular storage layer, not a measurement of hidden flash geometry. Do not infer application-level power-loss behavior from this field alone.",
  "status": "shipping",
  "advantages": [
    {
      "text": "Helps callers choose requests that cover complete physical sectors.",
      "citationIds": [
        "microsoft-buffering"
      ]
    }
  ],
  "limitations": [
    {
      "text": "Linux can synthesize the reported physical block size from component devices in a stacked configuration.",
      "citationIds": [
        "linux-abi"
      ]
    },
    {
      "text": "Torn-write protection requires a separately supported atomic-write contract.",
      "citationIds": [
        "linux-atomic"
      ]
    }
  ],
  "related": [
    "logical-sector",
    "advanced-format",
    "512e",
    "4kn-native",
    "partition-alignment",
    "power-loss-protection",
    "torn-write",
    "rwf-atomic"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "linux-abi",
      "title": "Linux 6.12: stable sysfs block ABI, sector sizes and I/O topology",
      "url": "https://raw.githubusercontent.com/torvalds/linux/v6.12/Documentation/ABI/stable/sysfs-block",
      "accessed": "2026-10-12"
    },
    {
      "id": "microsoft-buffering",
      "title": "Microsoft: File buffering, alignment and file access requirements",
      "url": "https://learn.microsoft.com/en-us/windows/win32/fileio/file-buffering",
      "accessed": "2026-10-12"
    },
    {
      "id": "linux-atomic",
      "title": "Linux ext4 documentation: Atomic Block Writes, requirements and semantics",
      "url": "https://docs.kernel.org/filesystems/ext4/atomic_writes.html",
      "accessed": "2026-10-12"
    },
    {
      "id": "hesela-sector-alignment",
      "title": "Hesela: 512e, 4Kn and alignment: geometry is not durability",
      "url": "https://hesela.com/analyses/sector-sizes-alignment-not-durability/",
      "accessed": "2026-10-12"
    }
  ],
  "updated": "2026-10-12"
}