Here's what I want, but haven't been able to find:

I already have a beefy server at home ( it's actually a refurbished enterprise workstation, with 24 cores, but read on ).

However it lacks drives. What I ideally want is a a dumb drive bay I could buy, and then connect ( somehow ) to my existing server, so I could use its CPU and RAM.

I don't want this drive bay to have its own CPU, I just want it to hold data and transfer it over some wire. Ideally I would achieve close to gigabit speeds requesting data off of this server/drive bay.

Some options I've explored are those dumb quad storage bays that connect over USB-3. But I was worried about running ZFS over a USB interface, as well as potentially parallel read and writes with the quality of the USB controller.