The work being done is addressing the deletes, AIUI, but of course there are other things happening during shutdown, too.There are no deletes to do. It was a clean index to begin with and there were no duplicates.
I have not followed this thread, so forgive me if this has already been suggested....
If you know that there are not any duplicates, have you tried indexing with allowDups=true?
It will not change the fsync cost, but it may reduce some other checking times.
ryan
