SMB2 + Mavericks

Since SMB2 is now the default protocol for LAN transfers on Mavericks, is there any way to force the Drobo and Mavericks (10.9) to connected using this protocol?

Time Machine is the only reason that AFP needs to be used still (for Apple’s own products, and the TM feature for the 5N).

I tried using SMB on my new Drobo 5N but for some reason I can still only get about half the data transfer speed that I can get on AFP. I still haven’t fathomed out why.