The author migrated away from Bcachefs due to persistent performance issues and instability despite extensive troubleshooting. While initially impressed with Bcachefs's features, they experienced slowdowns, freezes, and data corruption, especially under memory pressure. Attempts to identify and fix the problems through kernel debugging and communication with the developers were unsuccessful, leaving the author with no choice but to switch back to ZFS. Although acknowledging Bcachefs's potential, the author concludes it's not currently production-ready for their workload.
Kent Sesse, the author, details their experience migrating away from the experimental Bcachefs filesystem after encountering several issues that ultimately made it untenable for their production server. Initially drawn to Bcachefs due to its appealing features such as copy-on-write, compression, and checksumming, Sesse hoped it would offer performance improvements and data integrity benefits over their existing ext4 setup.
The migration process itself was described as relatively straightforward, involving creating a Bcachefs filesystem on a new partition and using rsync to copy data from the existing ext4 filesystem. However, problems arose soon after. Performance, contrary to expectations, was noticeably worse than with ext4, particularly in random read/write scenarios. This performance degradation became especially pronounced when the SSD caching layer filled up, leading to significant slowdowns.
The author further experienced disconcerting stability issues. The blog post recounts two instances of silent data corruption, where files became unreadable despite Bcachefs's built-in checksumming feature. This loss of data, although seemingly minor in terms of the files affected, eroded Sesse's trust in the filesystem's integrity. Additionally, the blog post mentions an incident involving a kernel panic directly attributable to Bcachefs. This kernel panic, along with a documented history of Bcachefs-related kernel crashes, contributed further to the decision to migrate away.
The final straw, leading to the immediate decision to switch back, was a catastrophic failure where the Bcachefs filesystem became completely corrupted and unmountable. This incident required Sesse to restore from a backup, highlighting the risks associated with using an experimental filesystem in a production environment.
Ultimately, despite the initial promise and the author's acknowledgment of Bcachefs's potential, the combination of poor performance, data corruption, kernel panics, and the catastrophic failure led to the decision to abandon Bcachefs and revert to a more stable and reliable ext4 filesystem. The author concludes by expressing disappointment but also understanding that Bcachefs is still under development and might not be suitable for production use at its current stage. They maintain some hope for the future of Bcachefs, suggesting they might reconsider it once it reaches a more mature state.
Summary of Comments ( 16 )
https://news.ycombinator.com/item?id=42773296
HN commenters generally express disappointment with Bcachefs's lack of mainline inclusion in the kernel, viewing it as a significant barrier to adoption and a potential sign of deeper issues. Some suggest the lengthy development process and stalled upstreaming might indicate fundamental flaws or maintainability problems within the filesystem itself. Several commenters express a preference for established filesystems like ZFS and btrfs, despite their own imperfections, due to their maturity and broader community support. Others question the wisdom of investing time in a filesystem unlikely to become a standard, citing concerns about future development and maintenance. While acknowledging Bcachefs's technically intriguing features, the consensus leans toward caution and skepticism about its long-term viability. A few offer more neutral perspectives, suggesting the author's experience might not be universally applicable and hoping for the project's eventual success.
The Hacker News post "Migrating Away from Bcachefs" (https://news.ycombinator.com/item?id=42773296) has a moderate number of comments discussing the author's experience with and decision to migrate from the Bcachefs filesystem. Many of the comments revolve around the perceived complexities and lack of mainstream adoption of Bcachefs, as well as alternative filesystems.
Several commenters expressed sympathy for the author's frustrations. One commenter mentioned their own difficulties compiling Bcachefs, highlighting the non-trivial process required to get it running. This sentiment was echoed by others, reinforcing the idea that Bcachefs isn't as user-friendly as more established filesystems. The complexities surrounding its checksumming features and lack of clear documentation were also mentioned as contributing factors to its perceived difficulty.
The discussion also touched upon the trade-offs between features and stability. Some commenters questioned the value of Bcachefs's advanced features, especially considering the potential for data loss or corruption that the author experienced. The inherent risks associated with using a less mature filesystem were weighed against the potential benefits, with some arguing that the stability of established solutions like ZFS or btrfs might be preferable for production environments.
A few commenters offered alternative filesystem suggestions, with ZFS and btrfs being the most frequently mentioned. The relative merits of each were debated, with some emphasizing ZFS's maturity and robustness, while others pointed to btrfs's lighter weight and integration with the Linux kernel. One commenter specifically mentioned XFS as another alternative, praising its stability and established track record.
The author themselves participated in the comments section, responding to questions and clarifying some points raised in the blog post. They acknowledged the experimental nature of Bcachefs and explained their rationale for choosing it initially. They also clarified the specific issues they encountered, which involved checksum mismatches and potential data corruption.
The overall tone of the comments is one of cautious curiosity about Bcachefs. While acknowledging its potential, many commenters expressed reservations about its complexity and lack of maturity. The discussion highlights the challenges faced by newer filesystems in gaining widespread adoption, especially when competing against well-established alternatives. The author's experience serves as a cautionary tale for those considering using Bcachefs in production environments, emphasizing the importance of thoroughly understanding the risks involved.