diff --git a/docs/btrfs-other.md b/docs/btrfs-other.md index 3b5982b..6546d87 100644 --- a/docs/btrfs-other.md +++ b/docs/btrfs-other.md @@ -11,28 +11,37 @@ bees has been tested in combination with the following: * Concurrent file modification (e.g. PostgreSQL and sqlite databases, build daemons) * all btrfs RAID profiles * IO errors during dedupe (read errors will throw exceptions, bees will catch them and skip over the affected extent) -* Filesystems mounted *with* the flushoncommit option (system crashes, power failures OK) +* Filesystems mounted *with* the flushoncommit option ([lots of harmless kernel log warnings on 4.15 and later](btrfs-kernel.md)) +* Filesystems mounted *without* the flushoncommit option * 4K filesystem data block size / clone alignment -* 64-bit and 32-bit host CPUs (amd64, x86, arm) +* 64-bit and 32-bit LE host CPUs (amd64, x86, arm) * Huge files (>1TB--although Btrfs performance on such files isn't great in general) * filesystems up to 30T+ bytes, 100M+ files * btrfs receive * btrfs nodatacow/nodatasum inode attribute or mount option (bees skips all nodatasum files) * open(O_DIRECT) (seems to work as well--or as poorly--with bees as with any other btrfs feature) +* lvmcache: no problems observed in testing with recent kernels or reported by users in the last year. Bad Btrfs Feature Interactions ------------------------------ bees has been tested in combination with the following, and various problems are known: -* bcache, lvmcache: **severe (filesystem-destroying) metadata corruption - issues** observed in testing and reported by users, apparently only when - used with bees. Plain SSD and HDD seem to be OK. +* bcache: no data-losing problems observed in testing with recent kernels + or reported by users in the last year. Some issues observed with + bcache interacting badly with some SSD models' firmware, but so far + this only causes temporary loss of service, not filesystem damage. + This behavior does not seem to be specific to bees (ordinary filesystem + tests with rsync and snapshots will reproduce it), but it does prevent + any significant testing of bees on bcache. + * btrfs send: there are bugs in `btrfs send` that can be triggered by bees. - The [`--workaround-btrfs-send` option](options.md) works around this issue, - but possibly at great cost. + The [`--workaround-btrfs-send` option](options.md) works around this issue + by preventing bees from modifying read-only snapshots. + * btrfs qgroups: very slow, sometimes hangs...and it's even worse when bees is running. + * btrfs autodefrag mount option: hangs and high CPU usage problems reported by users. bees cannot distinguish autodefrag activity from normal filesystem activity and will likely try to undo the autodefrag @@ -49,4 +58,5 @@ bees has not been tested with the following, and undesirable interactions may oc * btrfs out-of-tree kernel patches (e.g. in-kernel dedupe or encryption) * btrfs-convert from ext2/3/4 (never tested, might run out of space or ignore significant portions of the filesystem due to sanity checks) * btrfs mixed block groups (don't know a reason why it would *not* work, but never tested) -* Filesystems mounted *without* the flushoncommit option (don't know the data integrity impact of crashes during dedupe writes vs. ordinary writes) +* flashcache: an out-of-tree cache-HDD-on-SSD block layer helper. +* Host CPUs with exotic page sizes, alignment requirements, or endianness (ppc, alpha, sparc, strongarm, s390, mips, m68k...)