You don’t get a guarantee of write ordering from not just the disk (pretty much any kind) but the OS IO scheduler. Journaling filesystems can still implement a

You don’t get a guarantee of write ordering from not just the disk (pretty much any kind) but the OS IO scheduler. Journaling filesystems can still implement atomic appends with only metadata journaling. Updating in place is generally not atomic because of the way writeback works for buffered IO. If you use unbuffered IO you bypass the OS scheduler but still have the disk reordering things if you don’t use write barriers and they still don’t guarantee atomicity for regular writes.