It would be great if we could see journaling metrics in serverStatus(). It would be nice to be able to see from a remote client if we are using journaling. Beyond that it would be nice to see the LSN number just so we can track it when we see it in logs or whatever. Also for just testing/sanity it's nice to expose it.

Also, I am curious, when I see BackgroundFlushing information in serverStatus() when in journal mode does this now represent the stats for the O_direct flushes to the log, or does it still refer the fsync() of the data files? If the latter then it would be nice to have a similar section for the journal flush.

The use case I can image is that I could see that my response time to the place where I have the journal is slow and thus I could make the decision to move it to faster media and perhaps speed up my DB. But w/o those metrics, I am left to just try to make it as fast as possible w/o any real measures.