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f21569e88c
Fixing the obviously out-of-date and no-longer-tested things. Signed-off-by: Zygo Blaxell <bees@furryterror.org>
55 lines
2.8 KiB
Markdown
55 lines
2.8 KiB
Markdown
Good Btrfs Feature Interactions
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bees has been tested in combination with the following:
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* btrfs compression (zlib, lzo, zstd), mixtures of compressed and uncompressed extents
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* PREALLOC extents (unconditionally replaced with holes)
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* HOLE extents and btrfs no-holes feature
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* Other deduplicators, reflink copies (though bees may decide to redo their work)
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* btrfs snapshots and non-snapshot subvols (RW and RO)
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* Concurrent file modification (e.g. PostgreSQL and sqlite databases, VMs, build daemons)
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* All btrfs RAID profiles
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* IO errors during dedupe (read errors will throw exceptions, bees will catch them and skip over the affected extent)
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* Filesystems mounted with or without the `flushoncommit` option
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* 4K filesystem data block size / clone alignment
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* 64-bit and 32-bit LE host CPUs (amd64, x86, arm)
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* Large files (kernel 5.4 or later strongly recommended)
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* Filesystems up to 90T+ bytes, 1000M+ files
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* btrfs receive
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* btrfs nodatacow/nodatasum inode attribute or mount option (bees skips all nodatasum files)
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* open(O_DIRECT) (seems to work as well--or as poorly--with bees as with any other btrfs feature)
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* lvm dm-cache, writecache
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Bad Btrfs Feature Interactions
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------------------------------
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bees has been tested in combination with the following, and various problems are known:
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* btrfs send: there are bugs in `btrfs send` that can be triggered by
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bees on old kernels. The [`--workaround-btrfs-send` option](options.md)
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works around this issue by preventing bees from modifying read-only
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snapshots.
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* btrfs qgroups: very slow, sometimes hangs...and it's even worse when
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bees is running.
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* btrfs autodefrag mount option: bees cannot distinguish autodefrag
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activity from normal filesystem activity, and may try to undo the
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autodefrag if duplicate copies of the defragmented data exist.
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Untested Btrfs Feature Interactions
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-----------------------------------
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bees has not been tested with the following, and undesirable interactions may occur:
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* Non-4K filesystem data block size (should work if recompiled)
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* Non-equal hash (SUM) and filesystem data block (CLONE) sizes (need to fix that eventually)
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* btrfs seed filesystems (no particular reason it wouldn't work, but no one has reported trying)
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* btrfs out-of-tree kernel patches (e.g. in-kernel dedupe, encryption, extent tree v2)
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* btrfs-convert from ext2/3/4 (never tested, might run out of space or ignore significant portions of the filesystem due to sanity checks)
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* btrfs mixed block groups (don't know a reason why it would *not* work, but never tested)
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* Host CPUs with exotic page sizes, alignment requirements, or endianness (ppc, alpha, sparc, strongarm, s390, mips, m68k...)
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* bcache: used to be in the "bad" list, now in the "untested" list because nobody is rigorously testing, and bcache bugs come and go
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* flashcache: an out-of-tree cache-HDD-on-SSD block layer helper
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