Seagate ST4000LM024 Barracuda Compute 4TB 5400RPM SATA 6Gb/s 128MB Cache 2.5" Internal Hard Drive

This is the thickest 2.5" drive I've ever handled, but it operates quietly, and transfers files exactly as fast as expected.

This drive's power-draw is still low enough that it can be powered through USB, so if you make use of external USB to SATA adapters or drive bays, you shouldn't need the extra power adapter to run it!

Be warned that because of this drive's height of 15mm, it DOES NOT fit into a standard caddy that replaces the optical drive in laptops. Don't expect it to fit into most laptops at all, especially slim modern ones. Out of interest's sake, I tested for two laptops I own, neither could fit this drive, despite being older models and quite thick when compared to modern laptops.

Make very sure that your setup has enough clearance to accommodate it, otherwise it's a fantastic device. Recommended!