Has anyone tried bcachefs yet?

Discussion in 'Linux Admins, Storage and Virtualization' started by voxadam, Apr 22, 2018.

  1. voxadam

    voxadam Member

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    Kent Overstreet, the original developer of the bcache block caching system for Linux, has been developing bcachefs which he refers to as "The COW filesystem for Linux that won't eat your data" for awhile now and I was curious if anyone has had a chance to give it a spin.

    I've been running Btrfs on my primary workstation for a number of years without incident, though, the fact that I've avoided RAID5/6 like the plague probably has a lot to do with my success. I've been meaning to upgrade my primary SSD and do a clean install for awhile now and it's tempting to give bcachefs a shot. As bcachefs is based on the widely deployed and tested bcache code I'm reasonably confident in its stability but in the event it does eat my data I have backups. The primary thing that's holding me back is the lack of support snapshots which Kent freely admits is "by far the most complex of the remaining features to implement" and there's nary a mention of it on the TODO which worries me a bit.

    Anyway, I was just wondering if anyone had experimented with bcahcefs yet.

    Feature status:

    • Full data checksumming

      Fully supported and enabled by default. We do need to implement scrubbing, once we've got replication and can take advantage of it.

    • Compression

      Not quite finished - it's safe to enable, but there's some work left related to copy GC before we can enable free space accounting based on compressed size: right now, enabling compression won't actually let you store any more data in your filesystem than if the data was uncompressed

    • 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.

      Basic caching functionality works, but it's not (yet) as configurable as bcache's caching (e.g. you can't specify writethrough caching).

    • Replication

      All the core functionality is complete, and it's getting close to usable: you can create a multi device filesystem with replication, and then while the filesystem is in use take one device offline without any loss of availability.

    • 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

      Snapshot implementation has been started, but snapshots are by far the most complex of the remaining features to implement - it's going to be quite awhile before I can dedicate enough time to finishing them, but I'm very much looking forward to showing off what it'll be able to do.
    Known issues/caveats
    • Mount time

      We currently walk all metadata at mount time (multiple times, in fact) - on flash this shouldn't even be noticeable unless your filesystem is very large, but on rotating disk expect mount times to be slow. This will be addressed in the future - mount times will likely be the next big push after the next big batch of on disk format changes.

    homepage: bcachefs
    git: evilpiepirate.org/git/bcachefs.git
    Patreon: Kent Overstreet is creating bcachefs - a next generation Linux filesystem | Patreon
    mailing list: Majordomo Lists at VGER.KERNEL.ORG
    irc: irc://irc.oftc.net/#bcache
    The bcachefs filesystem [LWN.net] - 25 August 2015
    Bcachefs - encryption, fsck, and more - 15 March 2017
    A new bcachefs release [LWN.net] - 16 March 2017
     
    #1
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  2. MiniKnight

    MiniKnight Well-Known Member

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    I'm not ready to use it yet. I strongly prefer upstream kernel support. This also gives me pause
    That isn't giving me confidence.

    As a project, the concept has promise.
     
    #2
    voxadam likes this.
  3. dandanio

    dandanio New Member

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    I have dabbled when I was looking for alternatives for ZFS. But since Red Hat abandoned it in their distro, I scrapped all thoughts of playing with it again anytime in the future. ZFS is it and Btrfs has nothing to offer to make it superior to it.
     
    #3
  4. Joel

    Joel Active Member

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    From your description it sounds like it's basically trying to copy ZFS, so why not just use the original which is at least 15 years old and mostly mature?

    Of course for ultimate stability you'd want to stick with BSD OSes.
     
    #4
  5. dswartz

    dswartz Member

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    It's not really like ZFS at all. That said, it seems to share the weakness of a number of one-man projects I've seen in the past. The developer disappears for weeks at a time, incommunicado...
     
    #5
  6. SlickNetAaron

    SlickNetAaron Member

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    I’m hoping this takes off! The design, feature roadmap and performance look impressive on a cursory review
     
    #6
  7. dswartz

    dswartz Member

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    Yeah, that would be nice. I'm not holding my breath though. I've seen this WAY too many times before. One-man project. Too much stuff to do. Doesn't want to take others on board to help. Gets burned out and either disappears for weeks at a time, or just abandons the project (not saying he's done all of this, but enough warning signs to make me leery...)
     
    #7
  8. Joel

    Joel Active Member

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    Definitely not something I’d want in a file system, especially compared to a mature product like ZFS...
     
    #8
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