Nice article Perry, very informative. Maybe you can help me with a question I have. I'm looking for a way (in a DMV) to see how far the secondary replica has fallen behind under heavy database load (inserts, updates, deletes) on the primary. In other words, is there a way to see how many transactions the secondary needs to apply so it is caught up and in sync with the primary?

Also, is there an easy way to measure the overhead cost of using sync compared to async?