Bcachefs seems like it needs the attention of a team, not just one good dev. Since it's not even merged, I guess it's still 5 years out before we can use it..
I think it's already usable in a way that BεTRFS is not. Like it can be installed on modern kernels, and there are a handful of people using it as their root filesystem today.
I don't think it being out-of-tree is a huge deal per se. ZFS is also out-of-tree. For use on personal systems, I think the bigger thing is that the on-disk format is not officially stable/permanent yet. But if that comes before the thing is merged to the Linux kernel, I'd be willing to try it on a personal system.
Try it at your own risk, of course, but BCacheFS doesn't look like any extra work to set up on NixOS if you wanna try it there— if you tell NixOS that you wanna use bcachefs it'll just transparently pull in the required kernel for you.
Idk about filesystems development, but I agree that eventually it would be ideal for BCacheFS to have a sizeable development and maintenance team. Maybe in the early stages, though, it's good for it to have the kind of coherence and simplicity required to fit all in one person's head. Time will tell, I guess!
I have used it on NixOS for over a year on my main desktop and NAS box. The experience is .. flaky .. sometimes Kent does not have a new enough kernel version available that NixOS needs, there have been several major breakages where some background tasks spin at 100% cpu forever and the file system slows down to a crawl, sometimes you need a to run fsck from a compat branch to get your fs back into shape. At the moment my desktop is broken because the NixOS config forgot how to unlock my root volume. But when it works, it mostly stays out of my way. I think I will move to ZFS for my desktop, there has been just too much faff with my setup. The claim about there not being any on-disk data loss, IDK, I have read from disk some large media files that have been broken .. when they had been written during a slow crawl while the fs processes were spinning 100%. So jury is still out there.
I totally agree with some parent commenter here that it needs a team to work with Kent. Documentation is almost nonexistent (tho ArchWiki saves the day a little).
Oh yeah. ZFS is mature on a whole different level than BCacheFS, too. As a bystander and potential user, if I have a hope for BCacheFS it's once it makes it into the mainline kernel, it attracts more developers and grows into a community project with versioned releases and all that. I imagine that its author hopes the same.
