Archttp can not see the raid box through the USB instead of thunderbolt port. Archttp communicate to ARC-8050T3U through the Areca device driver but USB devices do not need any driver. This raid box can be managed through the ethernet port on the raid box. Regarding the low performance, you can refer the article below
https://support.apple.com/en-us/HT201163
Tags: ARC-8050T3U-12, Archttp