bcachefs VS bmap-tools

I'm keeping an eye on it but it's not there yet e.g. https://github.com/koverstreet/bcachefs/issues/619#issuecomm...

Bcachefs does not yet implement scrubs. Corrupted data can be detected, reading instead from a copy (if available). But the problems get neither reported nor fixed. So does not seem production ready yet...

https://github.com/koverstreet/bcachefs/issues/146

Clone a stable kernel-pve git tree, add as remote https://github.com/koverstreet/bcachefs Then merge the correct tree into the latest stable kernel-pve release.

I compiled https://github.com/koverstreet/bcachefs with the suggested instructions and did apt install -y bcachefs-tools linux-bcachefs after adding the bcachefs ppa. I then ran this script and was unable to mount https://gist.github.com/docfate111/135c130d38dd185c71d0b24ed41eb646 also when i was able to mount bcachefs qemu shows a segmentation fault and error about not recognizing filesystem

> But I recall reading elsewhere a discussion about some userspace program which did depend on holes being present in the filesystem as actual holes (visible to SEEK_HOLE and so on) and not as runs of zeros.

> treatment of on-disk segments as "what was written by programs" can cause areas of 0 to not be written by bmaptool copy

https://github.com/intel/bmap-tools/issues/75

IMO, the issue here isn't filesystem or zfs behavior, it's that bmap-tool wants an extra "don't care bit" per block, which filesystems (traditionally) don't track, and programs interacting with filesystem don't expect to exist.

Some of the comments I've made in this issue describe options to make things better.

(>_<) Oh man, I knew about [0] when I posted (which is why I said it just reduces the chance of hitting the bug (by a lot)). But after spending all Saturday JST on it, I went to bed before [1] was posted.

Skimming through #6958 though, it seems like it's the lesser of evils, compared to #15526... I think? It's less obvious (to me) what the impact of #6958 is. Is it silent undetectable corruption of your precious data potentially over years, or more likely to cause a crash or runtime error?

Reports like https://github.com/intel/bmap-tools/issues/65 make it seem more like the latter.

But I have to read more. But since the zfs_dmu_offset_next_sync setting was disabled by default until recently, I still suspect (but yeah, don't know for sure) that disabling is the safest thing we can currently do on unmodified ZFS systems.