Bcachefs

Bcachefs is a copy-on-write (COW) file system for Linux-based operating systems. Its primary developer, Kent Overstreet, first announced it in 2015, and efforts are ongoing to have it included in the mainline Linux kernel.[1][2][3] It is intended to compete with the modern features of ZFS or Btrfs, and the speed and performance of ext4 or XFS. It self-describes as "stable", as of December 2022.[4]

Bcachefs
Developer(s)Kent Overstreet
Introduced21 August 2015 (2015-08-21)
Structures
Directory contentsHybrid B+ tree
File allocationExtents
Bad blocksNone recorded
Features
Dates recordedmodification (mtime), attribute modification (ctime), access (atime), create (crtime)
AttributesExtended attributes
File system permissionsPOSIX (+ ACL in xattrs)
Transparent compressionYes
Transparent encryptionYes
Copy-on-writeYes
Other
Supported operating systemsLinux
Websitebcachefs.org

Features

Bcachefs is a copy-on-write (COW) file system for Linux-based operating systems.[5] Features include caching,[6] full file-system encryption using the ChaCha20 and Poly1305 algorithms,[7] native compression[6] via LZ4 and Zstandard,[8] snapshots,[6] CRC-32C and 64-bit checksumming.[5] It can span block devices, including in RAID configurations.[7]

Earlier versions of Bcachefs provided all the functionality of Bcache, a block-layer cache system for Linux, with which Bcachefs shares about 80% of its code.[1] As of December 2021, the block-layer cache functionality has been removed.[8]

History

Primary development has been by Kent Overstreet, the developer of Bcache, which he describes as a "prototype" for the ideas that became Bcachefs. Overstreet intends Bcachefs to replace Bcache.[1] Overstreet has stated that development of Bcachefs began as Bcache's developers realized that its codebase had "been evolving ... into a full blown, general-purpose POSIX filesystem", and that "there was a really clean and elegant design" within it if they took it in that direction. Some time after Bcache was merged in 2013 into the mainline Linux kernel, Overstreet left his job at Google to work full-time on Bcachefs.[5]

After a few years' unfunded development, Overstreet announced Bcachefs in 2015, at which point he called the code "more or less feature complete", and called for testers and contributors. He intended it to be an advanced file system with modern features[9] like those of ZFS or Btrfs, with the speed and performance of file systems such as ext4 and XFS.[5] As of 2017 Overstreet was receiving financial support for the development of Bcachefs via Patreon.[7]

As of mid-2018, the on-disk format had settled.[1] Patches had been submitted for review to have Bcachefs included in the mainline Linux kernel, but had not yet been accepted.[6]

By mid-2019, the desired features of Bcachefs had reached and associated patches to LKML was submitted for peer review. As of February 2023, Bcachefs has still not been merged into the mainline Linux kernel.[2][3] In May 2023, Bcachefs was once again submitted to the LKML.[10]

References
  1. Edge 2018.
  2. LKML 2021.
  3. LKML 2022.
  4. "bcachefs". bcachefs.org.
  5. Larabel 2015.
  6. Larabel 2018.
  7. Baader 2017.
  8. Overstreet, Kent (18 Dec 2021). "bcachefs: Principles of Operation" (PDF). Retrieved 10 May 2023.
  9. Jackson 2015.
  10. Larabel, Michael (10 May 2023). "Bcachefs Submitted For Review - Next-Gen CoW File-System Aims For Mainline". www.phoronix.com. Retrieved 10 May 2023.

Works cited
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