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These are simple on/off switches for the task queue. They are lightweight requests for bees to be paused temporarily, but allow bees to release open files and save progress while paused. These signals are an alternative to SIGSTOP and SIGCONT, or using the cgroup freezer's FROZEN and THAWED states, which pause and resume the bees process, but do not allow the bees process to release open files or save progress. Snapshot and file deletes can occur on the filesystem while bees is paused by SIGUSR1 but not by SIGSTOP. These signals are also an alternative to SIGTERM and restart, which flush out the whole hash table and progress state on exit, and read the whole table back into memory on restart. This feature is experimental and may be replaced by a more general configuration or runtime control mechanism in the future. Signed-off-by: Zygo Blaxell <bees@furryterror.org>
BEES
Best-Effort Extent-Same, a btrfs deduplication agent.
About bees
bees 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
Installation and Usage
Recommended Reading
- bees Gotchas
- btrfs kernel bugs - especially DATA CORRUPTION WARNING
- bees vs. other btrfs features
- What to do when something goes wrong
More Information
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 2015-2023 Zygo Blaxell bees@furryterror.org.
GPL (version 3 or later).