I am not sure I understand the point of having two local backup drives?
Simple - Redundancy. Although i do agree with the rest of ctyriders post, you've obviously made some good steps in setting up a solid backup but you do need some sort of offsite/cloud backup to be completely bomb-proof.
To do this you can keep a hard drive away from your home or you can set yourself up with a cloud backup service. I actually use two cloud backup services just in case one of them doesnt work/goes bust (Crashplan and Backblaze) i would recommend them both as reliable.
The best way to look at backups is never to put all your eggs in one basket, it's better to be over-prepared than not prepared enough. Here is my backup setup:
- Dropbox - Syncs my projects, documents and photo library to 2 other machines.
- Carbon Copy Cloner - creates a bootable usb clone of my boot drive once per week (which contains my dropbox, itunes library file, kindle downloads and Applications)
- Time Machine - runs from a 4 bay Drobo, backs up my boot drive and another external which contains my software iso rips and iTunes media.
- Backblaze and Crashplan - Does continuos cloud backups of everything already mentioned, plus about 5TB of my DVD/Bluray home rips (which are also on disc, but would be easier restoring from the web than reripping stuff)
Hope this gives you some ideas on where to go next