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db65031c2b
pthread_cancel doesn't really work properly. It was only being used in bees to bring threads to a stop if the BeesContext is destroyed early. It is frequently implicated in core dump reports because of the fragility of the C++ iostream / C stdio / library infrastructure, particularly surrounding upgrades on the host running bees. The pthread_cancel call itself often simply fails even when it doesn't call terminate(). Defer creation of the status and progress threads until after the BeesContext::start method is invoked. At that point, the existing ask-threads-nicely-to-stop code is up and running, and normal condvars can be used to bring bees to a stop, without having to resort to pthread_cancel. Since we're deleting half of the BeesContext constructor in this change, let's remove the other half too, and put an end to the deprecated support for multiple BeesContexts sharing a process. It's still possible to run multiple BeesContexts, but they will not share a FD cache. This will allow the FD cache's keys to become smaller and hopefully save some memory later on. Fixes: #171 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 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
- 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 2015-2018 Zygo Blaxell bees@furryterror.org.
GPL (version 3 or later).