I am going to build a PC and I want to have two HDD drives. One is going to be 4 TB for large file storage for music, content creation (Youtube/Twitch) and non demanding games possibly very few AAA games. The other drive is going to be a backup drive which will store the latest drive image as a compressed file in case it fails but I do not want to spend more than than necessary for its capacity. What size should I buy?