Biggest Linux Kernel Release Ever Welcomes bcachefs File System, Jettisons Itanium

Linux kernel 6.7 has been released, including support for the new next-gen copy-on-write (COW) bcachefs file system. The Register reports: Linus Torvalds announced the release on Sunday, noting that it is 'one of the largest kernel releases we've ever had.' Among the bigger and more visible changes are a whole new file system, along with fresh functionality for several existing ones; improved graphics support for several vendors' hardware; and the removal of an entire CPU architecture. The single biggest feature of 6.7 is the new bcachefs file system, which we examined in March 2022. As this is the first release of Linux to include the new file system, it definitely would be premature to trust any important data to it yet, but this is a welcome change. The executive summary is that bcachefs is a next-generation file system that, like Btrfs and ZFS, provides COW functionality. COW enables the almost instant creation of 'snapshots' of all or part of a drive or volume, which enables the OS to make disk operations transactional: In other words, to provide an 'undo' function for complex sets of disk write operations.

Having a COW file system on Linux isn't new. The existing next-gen file system in the kernel, Btrfs, also supports COW snapshots. The version in 6.7 sees several refinements. It inherits a feature implemented for Steam OS: Two Btrfs file systems with the same ID can be mounted simultaneously, for failover scenarios. It also has improved quota support and a new raid_stripe_tree that improves handling of arrays of dissimilar drives. Btrfs remains somewhat controversial. Red Hat banished it from RHEL years ago (although Oracle Linux still offers it) but SUSE's distros depend heavily upon it. It will be interesting to see how quickly SUSE's Snapper tool gains support for bcachefs: This new COW contender may reveal unquestioned assumptions built into the code. Since Snapper is also used in several non-SUSE distros, including Spiral Linux, Garuda, and siduction, they're tied to Btrfs as well.

The other widely used FOSS next-gen file system, OpenZFS, also supports COW, but licensing conflicts prevent ZFS being fully integrated into the Linux kernel. So although multiple distros (such as NixOS, Proxmox, TrueNAS Scale, Ubuntu, and Void Linux) support ZFS, it must remain separate and distinct. This results in limitations, such as the ZFS Advanced Read Cache being separate from Linux's page cache. Bcachefs is all-GPL and doesn't suffer from such limitations. It aims to supply the important features of ZFS, such as integrated volume management, while being as fast as ext4 or XFS, and also surpass Btrfs in both performance and, crucially, reliability. A full list of changes in this release can be viewed via KernelNewbies.

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