Linus Torvalds has approved the request to include the Bcachefs filesystem in the mainline of the Linux kernel and has added the Bcachefs implementation to the repository where the 6.7 kernel branch is being developed, with a release expected in early January. The patch added to the kernel includes about 95,000 lines of code. The project has been developed for over 10 years by Kent Overstreet, who also created the caching system for block devices on SSDs called Bcache.
Efforts to promote Bcachefs to the mainline began in 2020, after which nearly three more years were needed to eliminate comments and shortcomings identified during the review. This spring, an updated patch set was proposed, which was rejected several times but was ultimately accepted into the linux-next branch in September, intended for testing features for future Linux kernel releases.
Bcachefs is developed using technologies already tested in the development of the Bcache block device, intended for caching access to slow hard drives on fast SSDs (included in the kernel since version 3.10). Bcachefs employs a Copy-on-Write (COW) mechanism, where changes do not result in data overwrites — the new state is written in a new location, after which the pointer to the current state is updated.
Bcachefs attempts to achieve a combination of performance, reliability, and scalability characteristic of XFS, and the extended functionality available in Btrfs and ZFS, such as the inclusion of multiple devices in a partition, layered layouts of storage, replication (RAID 1/10), caching, transparent data compression (LZ4, gzip, and ZSTD modes), state snapshots, integrity verification using checksums, ability to store Reed-Solomon error correction codes (RAID 5/6), and storing information in encrypted form (using ChaCha20 and Poly1305). In terms of performance, Bcachefs outperforms Btrfs and other COW-based filesystems, demonstrating speeds close to Ext4 and XFS.
A distinctive feature of Bcachefs is the support for layered storage device connections, where the storage is composed of several layers — the bottom layer connects the fastest drives (SSDs), which are used to cache frequently accessed data, while the upper layer consists of larger and cheaper disks that provide storage for less frequently accessed data. Writeback caching mode can be applied between the layers. Drives can be dynamically added and detached from the partition without stopping the use of the file system (data migrates automatically).
Source: opennet.ru
