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31d26bcfc6
Split crawlers into two separate Tasks:
1. a Task which locates the next inode with a new data extent.
2. a Task which scans every new extent in that inode.
This simplifies some lock contention and execution ordering issues.
Files are read sequentially. Workers dynamically scale up or
down as needed, without creating thousands of deferred Task objects.
Workers obtain inode locks for different inodes in btrfs, so they
can work in parallel instead of waiting for each other.
This change in behavior comes with new names for the worker Tasks:
"crawl_master" is now "crawl_more", the singular Task which
creates inode-scanning Tasks.
"crawl_<subvol>" is now "crawl_<subvol>_<inode>".
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
- NEW Works around
btrfs sendproblems with dedupe and incremental parent snapshots - 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 2015-2022 Zygo Blaxell bees@furryterror.org.
GPL (version 3 or later).