IMO its better to do a scheduled sync's to the hdd array a few times a day. This leaves the SSD array running at full speed when you are using it PLUS it gives you time to recover files from the HDD array that wouldn't normally be available using a raid0+1 or raid10. Like accidental file deletions.
This is the exact method I use at home using robocopy. If my wife or kids accidentally delete one of their shows, I know I have until 3am to copy it back from the server. The best part is that Robocopy is a windows command (ie - you already have it free!) and works great! Synctoy didnt work so great after I switched to win8.