I've had my own bad experiences with Btrfs (it doesn't behave well when close to full), and my intuition is that Facebook's use of it is in a limited operational domain. It works well for their use case (uploaded media I think?), combined with the way they manage and provision clusters. Letting random users loose on it uncovers a variety of failure modes and fixes are slow to come.
On the other hand, while I haven't used it for /, dipping my toes in bcachefs with recoverable data has been a pleasant experience. Compression, encryption, checksumming, deduplication, easy filesystem resizing, SSD acceleration, ease of adding devices… it's good to have it all in one place.
> my intuition is that Facebook's use of it is in a limited operational domain
That's not really true: it's deployed across a wide variety of workloads. Not databases, obviously, but reliability concerns have nothing to do with that.
My point isn't "they use it, it must be good": that's silly. My point is that they employ multiple full time engineers dedicated to finding and fixing the bugs in upstream Linux, and because of that, BTRFS is more well tested in practice than anything else out there today.
It doesn't matter how well thought out or "elegant" bcachefs or ZFS are: they don't have a team of full time engineers with access to thousands upon thousands of machines running the filesystem actively fixing bugs. That's what actually matters.
> Compression, encryption, checksumming, deduplication, easy filesystem resizing, SSD acceleration, ease of adding devices... it's good to have it all in one place.
On the other hand, while I haven't used it for /, dipping my toes in bcachefs with recoverable data has been a pleasant experience. Compression, encryption, checksumming, deduplication, easy filesystem resizing, SSD acceleration, ease of adding devices… it's good to have it all in one place.