PRODUCT NAME: HGST Deskstar 3.5-Inch 2TB 7200RPM SATA III 6 Gbps 64 MB Cache Internal Hard Drive
PRODUCT NAME: Eaxer USB 3.0 Hard Drive Disk External Enclosure Case for 2.5 /3.5 inch SATA HDD and SSD
COMMENTS: I initially had a 4TB HP MyPassport that I previously owned and used for a temporary backup but it wasn't cutting it (and people did state they were having problems with MyPassport). After reading this thread I found people had some success with adding a USB Hard drive enclosure. I had a HGST hard drive that has been unused for the past 4 months as I had upgraded to a larger drive. I deleted the partition in Windows before adding it to the Eaxer enclosure (which is backwards compatible to USB 2.0) and then adding the enclosure to Tablo.
Performance has been excellent. No strange slow downs, skips, or other oddities with this setup. It should be noted that the enclosure supports 8TB and I may upgrade in the future. HGST makes quality drives that have low failure rates. Google BackBlaze HGST and they have solid stats on failure rates. I think this is a cost-effective superior solution as I have a faster 7200 hard drive that's less expensive than a purpose-built USB hard drive.
NOTE: The enclosure is not very well cooled. I recommend having it on its side to enhance cooling.
NOTE2: I didn't have success finding an inexpensive well-cooled enclosure that was backwards compatible with USB 2.0. I'll continue looking and update if I find something better. I did find one that was $56 dollars on NewEgg...that's as much as the drive!