Hi Folks. I have two 3TB external hard drives plugged into my iMac that need backing up (in case you are wondering the contents of the internal drive are largely backed up using Sugarsync). Everywhere post or article I read on the subject of backup says that your backup drive should be 2-3 times the size of the data you are backing up but this seems slightly impractical to me once you get to the 3TB stage. My current plan is to buy two 4TB hard drives one which will backup one of the external drives using time machine and the other which will back up the second external hard drive using 3rd party software. I am not that bothered about retaining lots of different versions of data. A single version is enough for me. With this in mind is my plan going to work? or is there something that I've failed to take into account? I want to check before i buy the drives as initially i failed to do any proper research regarding how to back up and stupidly bought 3TB drives to back up 3TB drives only to have time machine tell me it had insufficient space to backup.