mirror of
https://github.com/Zygo/bees.git
synced 2025-05-17 13:25:45 +02:00
f9a697518d
Binary searches can be extremely slow if the target bytenr is near a metadata block group, because metadata items are not visible to the binary search algorithm. In a non-mixed-bg filesystem, there can be hundreds of thousands of metadata items between data extent items, and since the binary search algorithm can't see them, it will run searches that iterate over hundreds of thousands of objects about a dozen times. This is less of a problem for mixed-bg filesystems because the data and metadata blocks are not isolated from each other. The binary search algorithm still can't see the metadata items, but there are usually some data items close by to prevent the linear item filter from running too long. Introduce a new fetcher class (all the good names were taken) that tracks where the end of the current block group is. When the end of the current block group is reached in the linear search, skip ahead to a block group that can contain data items. 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).