All elements of the controller PCB are visible on the image. On the upper left side you can see the eSATA connector, which is surrounded by a shielding metal. Below it you can see the SATA bridge. The controller obviously carries the RAID logic as well as a USB interface. The voltage regulators offer different operating voltages for the drives and the logic.
We were surprised that it is necessary to choose between RAID 0 and RAID 1. RAID 0 will increase performance considerably, but it will put your data at risk, since the data of both drives will be lost if only one fails. If RAID 1 is selected, data is mirrored onto both drives, but the net capacity is split in half. A just a bunch of drives (JBOD would be a suitable alternative, because it spans data across both drives. If one fails, the data on the second drive can be recovered.