If you just want an external drive, get an external drive. They're cheap.
If you need to be able to access multiple bare drives, the USB setup works (recommend a USB3 version), but there are internal SATA docks as well that can be set up for hot swapping, and fit into a 5.25" bay. I use one of those in my desktop, and it's a pretty decent setup that doesn't compromise stability or performance.
Canon 6D|24-105/4L |70-300/4-5.6 IS USM|50/1.4 USM|50/2.5 CM|50/1.8 STM|85/1.8 USM|Samyang/Bower 14/2.8|24/2.8 IS|Sigma 150-600 | C
Canon EOS-M|11-22 IS|22/2|EF-M 18-55