Bcachefs
| Developer(s) | Kent Overstreet |
|---|---|
| Introduced | 21 August 2015 |
| Structures | |
| Directory contents | Hybrid B+ tree |
| File allocation | Extents |
| Bad blocks | None recorded |
| Features | |
| Dates recorded | modification (mtime), attribute modification (ctime), access (atime), create (crtime) |
| Attributes | Extended attributes |
| File system permissions | POSIX (+ ACL in xattrs) |
| Transparent compression | Yes |
| Transparent encryption | Yes |
| Copy-on-write | Yes |
| Other | |
| Supported operating systems | Linux |
| Website | 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]
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, gzip[8] and Zstandard,[9] 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.[9]
On a data structure level, bcachefs uses B-trees like many other modern file systems, but with an unusually large node size defaulting to 256 KiB. These nodes are internally log-structured, forming a hybrid data structure, reducing the need for rewriting nodes on update.[10] Snapshots are not implemented by cloning a COW tree, but by adding a version number to filesystem objects.[11] The COW feature and the bucket allocator enables a RAID implementation with neither write hole nor IO fragmentation.[9]
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[12] 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, but did not make it into the 6.5 development kernel release.[13]
References
- ^ a b c d Edge 2018.
- ^ a b LKML 2021.
- ^ a b LKML 2022.
- ^ "bcachefs". bcachefs.org.
- ^ a b c d Larabel 2015.
- ^ a b c d Larabel 2018.
- ^ a b c Baader 2017.
- ^ https://bcachefs-docs.readthedocs.io/en/latest/options.html#compression-types [bare URL]
- ^ a b c Overstreet, Kent (18 Dec 2021). "bcachefs: Principles of Operation" (PDF). Retrieved 10 May 2023.
- ^ "Architecture". bcachefs.org.
- ^ "Snapshots". bcachefs.org.
- ^ Jackson 2015.
- ^ 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
- Baader, Hans-Joachim (2017-03-17). "Neue Version von Bcachefs bringt Verschlüsselung" [New version of bcachefs brings encryption]. Pro-Linux (in German). Retrieved 2018-11-23.
- Edge, Jake (2018-05-23). "An update on bcachefs". LWN.net. Archived from the original on 2018-06-01. Retrieved 2018-11-22.
- Jackson, Joab (2015-08-21). "Former Google engineer revs up a new Linux filesystem". PC World. Retrieved 2018-11-22.
- Larabel, Michael (2015-08-21). "A New Linux File-System Aims For Speed While Having ZFS/Btrfs-Like Features". Phoronix. Archived from the original on 2015-08-23. Retrieved 2018-11-22.
- Larabel, Michael (2018-05-09). "Bcachefs File-System Is Working On Going Upstream In The Linux Kernel". Phoronix. Archived from the original on 2018-07-09. Retrieved 2018-11-22.
- LKML (2019-06-10). "bcachefs status update (it's done cooking; let's get this sucker merged)". Linux Kernel Mailing List.
- LKML (2021-11-04). "bcachefs status update - current and future work". Linux Kernel Mailing List. Retrieved 2021-12-02.
- LKML (2022-02-16). "bcachefs". Linux Kernel Mailing List. Retrieved 2022-09-14.
