Hi, I have an iMac 27" with 1Tb HDD, and one WD 1Tb external USB drive using about 600gb, I need to back up those 600gb that are on the external drive, today I purchased another WD 1Tb external USD drive to use for backing up those files only, but looking on the internet it looks that TM doesn't back up files from an External HDD to another External HDD? how can't it be? is TM that bad? So I've 2 options: Option 1) using the new external HDD to back up the files that are on the used External HDD using another app instead of TM? (if so, which one could do this?) Option 2) returning the new 1Tb HDD I bought and get a 2Tb of capacity and use it for back up the internal iMac HHD plus the External HDD, can I use TM for this? Please help, I really need to back up those 600gb that are on my External HDD to another External HDD, much appreciated any suggestions! I'm amateur with back up, it would be the very first time doing this, and I'm Mac user for about 20 years!!! I know, bizarrreeeeeee.! I appreciate to get an answer asap please in order I have time to return and change the 1Tb HDD to 2Tb if it worth backing up everything!! thanks!