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Capture SIGINT and SIGTERM and shut down, preserving current completed crawl and hash table state. * Executing tasks are completed, queued tasks are paused. * Crawl state is saved. * The crawl master and crawl writeback threads are terminated. * The task queue is flushed. * Dirty hash table extents are flushed. * Hash prefetch and writeback threads are terminated. * Hash table is deallocated. * FD caches and tmpfiles are destroyed. * Assuming the above didn't crash or deadlock, bees exits. The above order isn't the fastest, but it does roughly follow the shared_ptr dependencies and avoids data races--especially those that might lead to bees reporting an extent scanned when it was only queued for future scanning that did not occur. In case of a violation of expected shared_ptr dependency order, exceptions in BeesContext child object accessor methods (i.e. roots(), hash_table(), etc) prevent any further progress in threads that somehow remain unexpectedly active. Move some threads from main into BeesContext so they can be stopped via BeesContext. The main thread now runs a loop waiting for signals. A slow FD leak was discovered in TempFile handling. This has not been fixed yet, but an implementation detail of the C++ runtime library makes the leak so slow it may never be important enough to fix. 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
- NEW Works around
btrfs sendproblems with dedupe and incremental parent shapshots - 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).