I don't know if it ever got better, but in 2015 I lost multiple BTRFS file systems that we operated at near capacity limit, with a hefty churn of files. The FS

I don't know if it ever got better, but in 2015 I lost multiple BTRFS file systems that we operated at near capacity limit, with a hefty churn of files. The FS wasn't shutdown without unmounting, or anything like that, but just used intensively. We had heard that you should keep plenty of unused space on BTRFS file systems, and this must be why. The file systems couldn't be restored with the official suite of tools. It was a backup anyway and we restored the data from secondary backup. I'm not positive that there is any other file system that I've ever lost significant data on.