Migrating Away from Bcachefs

Original Article ↗ Hacker News Discussion ↗

Status of bcachefs and Appropriate Use

  • Widely described as still “experimental”; several commenters say it belongs on test, cache, or gaming machines, not important data yet.
  • Some are waiting to migrate from ZFS or other filesystems but won’t risk main systems until it’s declared stable.
  • There is debate over how long “6 months to non‑experimental” has been claimed; some see stability timelines as optimistic.

User Experiences and Bug Handling

  • Multiple users report very fast bug fixes and positive direct interactions with the maintainer.
  • Others describe bug reporting as unpleasant or confrontational, enough to sap the “fun” out of experimentation.
  • There is tension between fixing issues quickly versus following slower, more conservative kernel processes.

Debian, Rust Dependencies, and Packaging Policy

  • Major thread around a Debian packaging incident:
    • Debian relaxed or altered Rust dependency versions and debundled libraries against upstream’s advice.
    • This allegedly broke builds and delayed critical fixes (e.g., mount options, degraded-mode mounting).
    • Users hit issues, but bug reports flowed to upstream rather than to the distro.
  • Some argue distros assume maintenance responsibility when they modify dependencies; others note, in practice, users still go upstream.
  • Upstream now strongly prefers no unbundling and is fine with delaying or avoiding inclusion in distros until things are more mature.
  • Suggested mitigation: clearly document supported versions, use issue templates, and aggressively close reports from unsupported package builds.

Filesystem Design, On-Disk Changes, and Upgrades

  • bcachefs is described as “a database under the hood,” easing some backward/forward compatibility.
  • Two recent impactful on-disk changes are discussed (accounting rewrite, backpointer changes) to improve extensibility and fsck scalability.
  • Several commenters like the idea of in-place large metadata/schema upgrades instead of “reformat and restore,” even if they take hours.

Comparisons with Other Filesystems

  • Some stick with ext4, XFS, or especially ZFS, citing battle-tested stability and aversion to data-loss risk.
  • A data corruption bug in ZFS’s history is noted but argued not to disqualify it from being “rock solid.”
  • XFS and ext4 inode behavior and small-file performance are debated; XFS’s dynamic inode allocation is praised, while ext4’s fixed inode count can be a limit in extreme small-file workloads.

Future and Governance Concerns

  • A few commenters predict bcachefs could be pulled from mainline if process and interpersonal issues persist with kernel maintainers.
  • Others emphasize that current rapid change is part of the experimental phase and appears to be stabilizing.