> Is there a reason for that?

I can give you mine. I was working with a Raspberry Pi 3, and using a USB SSD. It's a USB2 link, so a bit choked, and I figured, hey, filesystem compression can help here, btrfs supports it, great! And it helped - you could get "real world" disk reads a good bit faster than the USB2 bus speed.

Until one day, I rebooted, and it didn't come back up. Analysis on another system was that the btrfs filesystem was just... toast. I've no idea what happened, I found some stuff that said "Oh, uh... don't use btrfs over USB, it kinda breaks in some cases...", the recovery tools couldn't even decide that the filesystem was a btrfs filesystem, and, nope.

I put data on the filesystem, I expect it to come back. btrfs broke that guarantee with a Pi full of data (nothing too important, they're just scratch systems and light desktops), so... I now stick to the boring things like ext4 that have been exceedingly well proven. Is it the best filesystem out there in terms of features? Certainly not. Am I pretty darn sure that I'm not going to trip some edge case and totally scramble the filesystem? Yes, and that's what I care about.

Lots of us got burnt with data loss and aren’t willing to give it a chance again. Maybe it’s better now? I don’t have a reason to give it a second chance when there are plenty of stable alternatives that have saved my ass I’m the past instead of telling me I’m SOL.

That's exactly it. I've used btrfs in production since Ubuntu 10.04, at scale since 12.04, and had nothing but great experiences with it - especially with the seed volume functionality, which allowed me to build the foundation for a major container-as-a-service platform before Docker was a thing. btrfs never lost our data, but I've also seen way too many btrfs kernel panics that were clearly related to insufficiently mature filesystem code, and I can understand people who did lose data, got burned and never want to trust btrfs again.

In their earlier days, the ENOSPCE bug corrupts the filesystem.

If you do a heavy random write workload, it fills up the disk pretty quickly and require a re-balance _before_ ran out of space.

Of cause you can do nocow on those files, but than it lost all the checksuming/snapshotting features.

For me, it was https://bugzilla.kernel.org/show_bug.cgi?id=85581. Yes this endless-write loop is long fixed, but, given that something with 99% similar symptoms has surfaced in kernel 5.16 (or was this original bug not fixed properly?), I would say no.

It is a complex beast. It needs some maintenance and performance will degrade without it.

I've never lost data to it, I've never tried the soft RAID modes it has though, but I've experienced it making a system almost unusably slow. SUSE out of the box with it automates a lot of it and it's pretty remarkable. Transactional mode if you want it seems like a game changer for some servers and the snapper stuff has saved my bacon a couple times. It's getting there but like I said, it needs some maintenance and just formatting a partition with it is likely the wrong way to experience it.

For me, when I tried btrfs (which was about 10 years ago now) I discovered it was extremely slow. And not like 50% slower—when I switched to ext4 or xfs on the same disk with the same data I was getting a 10x or so speedup.

AFAIK it's not so bad in single-device use-cases. I think most of the more recent failures I've heard about have all had to do with Btrfs RAID. The prevailing wisdom still seems to be that if you want to use RAID, use an md soft-RAID device or LVM under your single-device Btrfs filesystem.

Yes, the only real problems are edge cases. I use it all the time.

BTRFS was marked stable in 2012 yet it still has abysmal performance compared to zfs, ext4, xfs, etc.