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# "The COW filesystem for Linux that won't eat your data".
Bcachefs is an advanced new filesystem for Linux, with an emphasis on
reliability and robustness and the complete set of features one would expect
from a modern filesystem.
* Copy on write (COW) - like zfs or btrfs
* Full data and metadata checksumming
* Multiple devices
* Replication
* Erasure coding (only feature not quite stable)
* Caching
* Compression
* Encryption
* Snapshots
* Scalable - has been tested to 50+ TB, will eventually scale far higher
* Already working and stable, with a small community of users
We prioritize robustness and reliability over features and hype: we make every
effort to ensure you won't lose data. It's building on top of a codebase with a
pedigree - bcache already has a reasonably good track record for reliability
(particularly considering how young upstream bcache is, in terms of engineer
man/years). Starting from there, bcachefs development has prioritized
incremental development, and keeping things stable, and aggressively fixing
design issues as they are found; the bcachefs codebase is considerably more
robust and mature than upstream bcache.
Fixing bugs always take priority over features! This means getting features out
takes longer, but for a filesystem not losing your data is the biggest feature.
Developing a filesystem is also not cheap or quick or easy; we need funding!
Please chip in on [[Patreon|https://www.patreon.com/bcachefs]] - the Patreon
page also has more information on the motivation for bcachefs and the state of
Linux filesystems, as well as some bcachefs status updates and information on
development.
If you don't want to use Patreon, I'm also happy to take donations via paypal:
kent.overstreet@gmail.com.
Join us in the bcache IRC channel, we have a small group of bcachefs users and
testers there: #bcache on OFTC (irc.oftc.net).
## Getting started
Bcachefs is not yet upstream - you'll have to build a kernel to use it.
First, check out the bcache kernel and tools repositories:
git clone https://evilpiepirate.org/git/bcachefs.git
git clone https://evilpiepirate.org/git/bcachefs-tools.git
Build and install as usual - make sure you enable `CONFIG_BCACHE_FS`. Then, to
format and mount a single device with the default options, run:
bcachefs format /dev/sda1
mount -t bcachefs /dev/sda1 /mnt
For a multi device filesystem, with sda1 caching sdb1:
bcachefs format /dev/sd[ab]1 \
--foreground_target /dev/sda1 \
--promote-target /dev/sda1 \
--background_target /dev/sdb1
mount -t bcachefs /dev/sda1:/dev/sdb1 /mnt
This will configure the filesystem so that writes will be buffered to /dev/sda1
before being written back to /dev/sdb1 in the background, and that hot data
will be promoted to /dev/sda1 for faster access.
See `bcachefs format --help` for more options.
## Documentation
We now have a user manual: [[bcachefs-principles-of-operation.pdf]]
## Status
Bcachefs can currently be considered beta quality. It has a small pool of
outside users and has been stable for quite some time now; there's no reason
to expect issues as long as you stick to the currently supported feature set.
It's been passing all xfstests for well over a year, and serious bugs are rare
at this point. However, given that it's still under active development backups
are a good idea.
### Feature status
- Full data checksumming
Fully supported and enabled by default; checksum errors will cause IOs to be
retried if there's another replica available.
- Compression
Done - LZ4, gzip and ZSTD are currently supported. ZSTD support unfortunately
still seems to be slightly buggy, but LZ4 is stable and well tested.
- Multiple device support
Done - you can add and remove devices at runtime while the filesystem is in
use, migrating data off the device if necessary.
- Tiering/writeback caching:
Bcachefs allows you to specify disks (or groups thereof) to be used for
three categories of I/O: foreground, background, and promote. Foreground
devices accept writes, whose data is copied to background devices
asynchronously, and the hot subset of which is copied to the promote devices
for performance.
- Replication (i.e. RAID1/10)
Done - you can yank out a disk while a filesystem is in use and it'll keep
working, transparently handling IO errors. You can then use the rereplicate
command to write out another copy of all the degraded data to another device.
- Erasure coding
Not quite stable
- [[Encryption]]
Whole filesystem AEAD style encryption (with ChaCha20 and Poly1305) is done
and merged. I would suggest not relying on it for anything critical until the
code has seen more outside review, though.
- Snapshots
Done, still shaking out a few bugs
|
