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bf6ae80eee
BeesRoots::transid_max_nocache calls btrfs_get_root_transid() which retrieves the transid of the root of the given Fd. Since the FS_TREE (subvol 5) is the root of the subvol hierarchy, it will always have the highest transid on the filesystem, and we do not need to look at any others. Also fix a bug where we pass BTRFS_FS_TREE_OBJECTID instead of the file descriptor root_fd() to btrfs_get_root_transid(). If BEESHOME is somewhere on the same btrfs filesystem, and there are no leaked FDs at bees startup, then BTRFS_FS_TREE_OBJECTID (5) usually has the same integer value as a valid file descriptor of some object on the filesystem that has a regularly increasing transid value. If Fd 5 happens to be a file in BEESHOME then bees itself drives the transid increments. This, combined with the search of all subvol roots, hides the bug (unless Fd 5 gets closed somehow). 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)
- Incremental realtime dedupe of 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
- Runs continuously as a daemon - no quick start/stop
- 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
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 2015-2018 Zygo Blaxell bees@furryterror.org.
GPL (version 3 or later).