Indeed, Btrfs is uniquely capable and important. It has lightweight snapshots of directory trees, and fully supports NFS exports and kernel namespaces, so it can easily solve technical problems that currently can't be easily solved using ZFS or other filesystems. Btrfs is also used now for ChromeOS's Crostini Linux application container.

Notable: Btrfs is used for all of ChromeOS and the crostini container is just another volume.

It's incredibly robust, really confusing why RH would be pulling this.

It was never emphasized, and probably rarely used by their customers. Prior RHEL release used ext4, then xfs by default. People who run RHEL don't want to think about what filesystem to use. They want standard, stable, reliable -- not dozens of options and features.

When you're pushing the container stuff, Btrfs becomes extraordinarily valuable. Being able to snapshot a base thing and then layer on top, and do trivial rebasing, as well as cheap replication of container volumes is _very_ useful.

On my Fedora and EL7 systems, I use Btrfs for the OS and for my containers for those purposes. It's awesome.

Slight correction: we use btrfs for the disk image backing the user's crostini state only. The rest of Chrome OS, and the crostini VM rootfs, still use ext4.

bcachefs is another "competitor" to btrfs: https://bcachefs.org/

But Redhat is going all in with stratis: https://stratis-storage.github.io/

I know, that broke libguestfs too :-( Btrfs was the only Linux filesystem that let me create an 8 exabyte virtual filesystem in a reasonable time.

https://rwmj.wordpress.com/2018/09/05/nbdkit-for-loopback-pt...

What's the use case for an 8 exabyte virtual file system?

Testing the limits :-) It's interesting because it shows you how things scale, and that information is useful even for normal-but-large filesystems. I've submitted a talk about this to FOSDEM next year.

Do they include other file systems which can provide data checksums? The linked stratis doesn't seem to have that feature, did they patch the underlying XFS? There don't seem to be that many filesystems with that capability yet:

https://en.wikipedia.org/wiki/Comparison_of_file_systems#Fil...

No, they plan to implement dm-integrity target as one of available dm layers.

See section 9.2.2 in https://stratis-storage.github.io/StratisSoftwareDesign.pdf

If it's only been "solid over the last year" it ain't solid.

I guess it depends on what Btrfs features you are using. I remember SUSE who are using Btrfs as a root fs in the enterprise distro restricting its use to a subset they consider stable.

On the Btrfs status page https://btrfs.wiki.kernel.org/index.php/Status you can see that the developers themselves consider several features "mostly ok", which is probably not an assessment most filesystem users will find reassuring.

I would actually be okay with Red Hat applying the same restriction SUSE did.

For what it's worth, this is the feature set SUSE offers: https://www.suse.com/releasenotes/x86_64/SUSE-SLES/15/#TechI...

I would be absolutely okay if Red Hat applied the same restrictions.

Has SuSE turned these off, or are they going to tell you "you shouldn't have used this feature" when you go for support?

They are switched off. You can't use them. They patch btrfs-progs to prevent accessing those features.

Previous Hacker News thread https://news.ycombinator.com/item?id=14907771

Really not an expert here but Red Hat did acquire and open source VDO from Permabit which has similar functionality AIUI.

I use subvolumes, snapshots, and send/recv functionality for cheap replication of data. Sometimes even on RAIDed disks!

There are only two file systems with that feature set today: Btrfs and ZFS. I personally prefer Btrfs because it's way more flexible and shipped with the Linux kernel.

As far as I know VDO only provides compression and deduplication. So no snapshots like in Btrfs and ZFS, although you can use LVM snapshots. Also no RAID features.