system/bees/README


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bees (Best-Effort Extent-Same) is a block-oriented userspace
deduplication agent designed for 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 and matching algorithms - can use as
    little as 1 GB hash table per 10 TB unique data (0.1GB/TB)
  * Daemon incrementally dedupes new data using btrfs tree search
  * Works with btrfs compression - dedupe any combination of compressed
    and uncompressed files
  * Works around btrfs filesystem structure to free more disk space
  * Persistent hash table for rapid restart after shutdown
  * Whole-filesystem dedupe - including snapshots
  * Constant hash table size - no increased RAM usage if data set
    becomes larger
  * Works on live data - no scheduled downtime required
  * Automatic self-throttling based on system load

Weaknesses:
  * Whole-filesystem dedupe - has no include/exclude filters, does not
    accept file lists
  * Requires root privilege (or CAP_SYS_ADMIN)
  * First run may require temporary disk space for extent reorganization
  * First run may increase metadata space usage if many snapshots exist
  * Constant hash table size - no decreased RAM usage if data set
    becomes smaller
  * btrfs only

After installing, edit /etc/rc.d/rc.bees.conf, /etc/logrotate.d/bees,
and /etc/bees/*.conf, and ensure /etc/rc.d/rc.bees is started from
/etc/rc.d/rc.local. To drastically reduce the amount of logging it is
recommended to add "-v 6" to OPTIONS in /etc/bees/*.conf.