Just so anyone else has this issue, I know I'm bringing back a zombie but there are still folks like me who are still buying these cards SAS2LP-MV8 and having issues.
Following are my experience:
The storport driver does not allow spin down regardless of OS. I've tried windows 7, windows server 2012 and windows home server.
I have tried the IPM Configuration fix to enable the "enableIdlePowerManagement" for storport drivers from the MSDN article. I can confirm that the registry key is created after a restart. This however also does not work.
I should add that I'm on the latest firmware and all SAS addresses of both cards in my system are identical.
The only solution that will allow native windows spin down is to install the windows XP/2003 miniport driver instead. This will allow native spin down to work.
Thankfully, with the miniport driver, things work in windows7/8/server 2012 so it should function for years to come. Performance deltas are unknown as of now but I have read that performance is not degraded.
Oh and don't bother contacting supermicro support. It will be a waste of your time.
Hope this helps.
Borna.