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5fe89d85c3
There's a pathological case where all of the extent scan crawlers except one are at the end of a crawl cycle, but the one crawler that is still running is keeping the Task queue full. The result is that bees never starts the other extent scan crawlers, because the queue is always full at the instant a new transid triggers the start of a new scan. That's bad because it will result in bees falling behind when new data from the inactive size tiers appears. To fix this, check for throttling _after_ creating at least one scan task in each crawler. That will keep the crawlers running, and possibly allow them to claw back some space in the Task queue. It slightly overcommits the Task queue, so there will be a few more Tasks than nominally allowed. Also (re)introduce some hysteresis in the queue size limit and reduce it a little, so that bees isn't continually stopping and restarting crawls every time one task is created or completed, and so that we stay under the configured Task limit despite overcommitting. 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 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_ADMINplus the usual filesystem read/modify caps) - 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 for old kernels
- 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 2015-2025 Zygo Blaxell bees@furryterror.org.
GPL (version 3 or later).