Comment by liendolucas | Hacker News Reader

Comment by liendolucas | Hacker News Reader

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I think the main issue with ZFS is that you need to learn a lot of concepts to actually understand how to do things correctly and don't fuck up.

To this day I've written some personal notes as warning reminders to be careful about certain operations. I can't remember the exact terminology (I believe these are called "attributes" or "features" in ZFS), but what happened to me not long ago was that if I created a ZFS filesystem (along with a pool) from Ubuntu it was creating some of these features that ZFS on FreeBSD didn't properly recognize and didn't allowed me to successfully mount it.

The other way round creating it from FreeBSD and then mounting it on Ubuntu worked as expected. The thing with these "features" is that they can be "promoted" or "upgraded" and in this case if you do so will again render the ZFS unavailable to be mounted in FreeBSD. I spent a whole day on this until for some reason I decided to print this list and effectively compare and do some online search about it.

> if I created a ZFS filesystem (along with a pool) from Ubuntu it was creating some of these features that ZFS on FreeBSD didn't properly recognize and didn't allowed me to successfully mount it.

I mean... shrugs ...you could format it as XFS and not be able to mount on FreeBSD either? Seems like feature flags is a good way to solve this problem.

I was actually going to ask that... Is XFS a good "portable" filesystem across GNU/Linux and different BSD flavors? Native support or through FUSE? The use case are USB drives. I don't mind losing visibility on Windows or MacOS, just to work flawlessly between these without major efforts.

Edit: Added some comments.

ZFS is really one of the only games in town AFAIK for serious filesystems. UFS might also work? Of course there is always exFAT, etc.

I could be wrong but I didn't go with UFS because apparently there are significant implementation differences among BSDs. I was kind of surprised to discover that.

FreeBSD and NetBSD essentially derive from the same source, 4.4BSD-Lite from March 1994. OpenBSD is a fork of NetBSD from 1995.

There's been a lot of divergence, and there's not really anything pushing towards convergence. FreeBSD modified UFS to meet their needs and desires and other BSDs went in other directions. There wasn't a lot of clammoring for a disk based data format for data interchange, so there's not a big reason to keep the divergent UFSes compatible. Exchange data via networks or tape archives or tars written to block devices or tarfiles on a widely recognized filesystem (msdos fat will do).

This pattern of a shared source and divergent development isn't super common. It's pretty rare commercially, and few opensource projects have forks that diverge and stay active for decades.

As a BSD user I think the divergence is a good thing. it means there are substantial differences which allows you to pick an OS that's really tailored to your usecase.

In the Linux world there's mainly just userland differences. I like it the BSD way. Of course Linux sees much more commercial input which I consider a bad thing and one reason I use FreeBSD so much. But for commercial interests it's a good thing to have as much in common as possible to have more potential customers.

The BSDs support ext2fs in kernel, that should work. FAT would work too of course.

You would probably not encounter that issue these days since FreeBSD 13 switched out the old FreeBSD ZFS tree in favor of the same OpenZFS you'd get on Linux https://cgit.freebsd.org/src/commit/?id=9e5787d2284e

The other comments already covered this, but yes, that is arguably the correct use of features: only enable the features (many of which can only be set at file system creation time; others can be upgraded to in a one way direction) that are supported by your target hosts.

At the time you last ran it (also said by sibling comment), FreeBSD still had not yet ran upstream OpenZFS, and still ran their own older code. To have had FBSD compatibility at the time, you would have had to only enable the features FBSD supported.

Generating the file system on FBSD, and not running "zfs upgrade" on Ubuntu would be one way of doing this, to avoid having to manually set features at all.

Today this is not an issue, everyone runs the same code.

You can read more about ZFS compatibility here for example:

- https://vermaden.wordpress.com/2022/03/25/zfs-compatibility/

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