| Chunk | A segment of a file, up to 64 MiB — the atomic unit of storage in LeilFS. |
| Chunkserver | A storage node that holds chunk data on its local disks. |
| CRC32 | 32‑bit cyclic redundancy check, stored per block to detect bit‑rot in stored data. |
| EC / Erasure Coding | A data‑protection scheme using Reed‑Solomon codes to reconstruct data from a subset of shards, giving redundancy at lower overhead than full copies. |
| FSAL | Filesystem Abstraction Layer — the NFS‑Ganesha plugin mechanism used to export LeilFS over NFS. |
| FUSE | Filesystem in Userspace — the Linux interface sfsmount uses to present LeilFS as a POSIX mount. |
| Goal | A policy defining how many copies (or EC shards) of each chunk must exist, and optionally where. |
| Inode | A metadata record representing a file or directory in the namespace. |
| Master | The active metadata server. Exactly one is active per cluster at any time. |
| Metalogger | A daemon that archives the master's metadata changelogs as an independent backup; it never becomes master. |
| mTLS | Mutual TLS — both ends of a connection authenticate with certificates. |
| Shadow master | A hot‑standby metadata server that receives changelogs in real time and can become the master (via uRaft or manual promotion). |
| Snapshot | A copy‑on‑write, point‑in‑time copy of a file or directory. |
| SPLIT format | A chunk‑storage format that separates chunk metadata from chunk data (e.g. metadata on NVMe), introduced in v4.0.0. |
| Topology | Network rack/datacenter assignment used for failure‑domain‑aware chunk placement and nearest‑replica reads. |
| Trash | A holding area where deleted files are retained for their trashtime before permanent removal. |
| uRaft | LeilFS's Raft consensus implementation, used to elect the active master for automatic failover. |