BEES
====

Best-Effort Extent-Same, a btrfs deduplication agent.

About bees
----------

bees is a block-oriented userspace deduplication agent designed to scale
up to large btrfs filesystems.  It is an offline dedupe combined with
an incremental data scan capability to minimize time data spends on disk
from write to dedupe.

Strengths
---------

 * Space-efficient hash table - can use as little as 1 GB hash table per 10 TB unique data (0.1GB/TB)
 * Daemon mode - incrementally dedupes new data as it appears
 * Largest extents first - recover more free space during fixed maintenance windows
 * Works with btrfs compression - dedupe any combination of compressed and uncompressed files
 * Whole-filesystem dedupe - scans data only once, even with snapshots and reflinks
 * Persistent hash table for rapid restart after shutdown
 * Constant hash table size - no increased RAM usage if data set becomes larger
 * Works on live data - no scheduled downtime required
 * Automatic self-throttling - reduces system load
 * btrfs support - recovers more free space from btrfs than naive dedupers

Weaknesses
----------

 * Whole-filesystem dedupe - has no include/exclude filters, does not accept file lists
 * Requires root privilege (`CAP_SYS_ADMIN` plus the usual filesystem read/modify caps)
 * [First run may increase metadata space usage if many snapshots exist](gotchas.md)
 * Constant hash table size - no decreased RAM usage if data set becomes smaller
 * btrfs only

Installation and Usage
----------------------

 * [Installation](install.md)
 * [Configuration](config.md)
 * [Running](running.md)
 * [Command Line Options](options.md)

Recommended Reading
-------------------

 * [bees Gotchas](gotchas.md)
 * [btrfs kernel bugs](btrfs-kernel.md) - especially DATA CORRUPTION WARNING for old kernels
 * [bees vs. other btrfs features](btrfs-other.md)
 * [What to do when something goes wrong](wrong.md)

More Information
----------------

 * [How bees works](how-it-works.md)
 * [Missing bees features](missing.md)
 * [Event counter descriptions](event-counters.md)

Bug Reports and Contributions
-----------------------------

Email bug reports and patches to Zygo Blaxell <bees@furryterror.org>.

You can also use Github:

        https://github.com/Zygo/bees

Copyright & License
-------------------

Copyright 2015-2025 Zygo Blaxell <bees@furryterror.org>.

GPL (version 3 or later).
