btrfs isn't journalled, but all the same, the issue is data integrity in a crash scenario. That will affect btrfs, and frankly, any other filesystem (for exampl

btrfs isn't journalled, but all the same, the issue is data integrity in a crash scenario. That will affect btrfs, and frankly, any other filesystem (for example ext2 or ext4-without-journal); imagine if an application depended on syncing files at certain points and the underlying storage stack decided to write out a "sync2" before "sync1" was written out.