PolicyFS (pfs)
PolicyFS is a Linux FUSE storage daemon that unifies multiple storage paths under one mountpoint with explicit read/write routing rules, an optional SQLite metadata index, and built-in maintenance jobs.
When you would use it
- You want a single mountpoint over multiple storage paths.
- You want explicit read/write routing rules.
- You want HDD-friendly directory listings using an index (SQLite) to avoid spinning up disks.
Why PolicyFS?
While tools like mergerfs are great for pooling drives, PolicyFS is focused on making storage behavior explicit:
- How reads and writes are routed.
- How metadata can be served without touching slow disks.
- How and when data should be moved to the archive tier.
Key Advantages
-
Policy-based routing: Route reads and writes based on path patterns, with clear write target selection (
first_found,most_free,least_free). -
SQLite-backed metadata index (optional): For storage paths with
indexed: true, metadata operations (e.g.,readdir,getattr) are served from SQLite. This reduces disk touches for metadata-heavy workloads. -
Built-in maintenance jobs: Indexing, moving, and applying deferred mutations are first-class CLI commands (
pfs index,pfs move,pfs prune,pfs maint) with systemd units. -
Portable data layout: Your data stays on normal Linux filesystems as plain files and directories.