High Point RocketU Quad USB 3.0 for Mac works great. I use it primariy with VMware Fusion on Mountain Lion.
Was having troubles with conflicts with CD/DVD Drive when Mirroring 2 Seagate GoFlex 2TB Drives. Downloading current driver resolved the issue.
I worked with High Point support. Quick response and excellent experience.
You may want to mount the drive in Slot 4.