Comment by throwaway8941

It's worthy of note that log-structured and copy-on-write filesystems (which I've seen described as two types of journaling) like btrfs and F2FS log data as part of their normal operation without any performance loss, so you always get a consistent view of the filesystem (barring bugs in the FS code or fsync-is-not-really-an-fsync treachery from your hardware).