Key terms used throughout the UFFS documentation.
| Term | Definition |
|---|---|
| ADS | Alternate Data Stream — NTFS feature allowing multiple data streams per file. Hidden from Explorer by default. Use --full to index them. |
| Allocated size | The actual disk space consumed by a file, rounded up to the nearest cluster boundary. Also called "size on disk". See Concepts §1. |
| Bulkiness | The ratio of allocated size to logical size, expressed as a percentage. A measure of allocation waste. 100 = perfectly efficient. See Concepts §3. |
| Cluster | The smallest unit of disk allocation in NTFS. Typically 4 KB (4096 bytes). Files smaller than one cluster still consume one full cluster. |
| Compact index | UFFS's in-memory representation of the MFT — a struct-of-arrays layout optimised for search and aggregation. |
| Daemon | The UFFS background process that holds the MFT index in memory and serves search queries over IPC. See Daemon. |
| DataFrame | A Polars columnar data structure. UFFS uses DataFrames internally for query execution. |
| Descendants | The total number of files and subdirectories inside a directory (recursive count). See Concepts §5. |
| Extension record | An MFT record that continues the attributes of another record. Used when a file has many hard links or ADS entries. Indexed in --full mode. |
| FRS | File Reference Segment — the MFT record number uniquely identifying a file or directory on a drive. Also called "file reference number". |
| Hard link | An NTFS feature allowing multiple directory entries to point to the same file data. The file has one FRS but multiple names and parent directories. |
| Idle retirement | The daemon's automatic shutdown after being idle for a configurable period (default: 2 hours). |
| .iocp | UFFS's serialised binary cache format. Stores a parsed MFT index for fast daemon startup. See Cache & Data Sources. |
| IPC | Inter-Process Communication — the local socket (Unix domain socket on macOS/Linux, named pipe on Windows) used between CLI and daemon. |
| Logical size | The actual data size of a file in bytes, independent of disk allocation. The number you see in Size columns. |
| MCP | Model Context Protocol — an open standard for AI agent tool integration. UFFS exposes an MCP server for filesystem search. See MCP. |
| MFT | Master File Table — the central metadata database of an NTFS volume. Contains one record per file/directory with name, size, timestamps, and attributes. |
| MFT bitmap | A bitmap indicating which MFT records are in use. UFFS uses this to skip free records (faster reads). Disabled with --no-bitmap. |
| NDJSON | Newline-Delimited JSON — one JSON object per line. UFFS's --format json output format. |
| Parquet | Apache Parquet — a columnar file format. UFFS can export the MFT to Parquet (daemon-managed, or via the uffs-mft tool) for external analysis. |
| Path resolution | The process of reconstructing full file paths from MFT data. The MFT stores only filenames and parent FRS numbers, not full paths. UFFS's FastPathResolver walks the parent chain. |
| Reparse point | An NTFS feature for symlinks, junctions, and volume mount points. Detected via the reparse attribute flag. |
| SoA | Struct of Arrays — a data layout where each field is stored in a separate contiguous array. UFFS uses SoA for the compact index, enabling SIMD-friendly scans. |
| Treesize | The recursive logical size of a directory subtree — the sum of sizes of all files in the directory and its descendants. See Concepts §4. |
| Tree allocated | Same as treesize but for allocated (on-disk) sizes. |