Thanks for the information Steve. I have a similar, but different set-up, probably not as comprehensive as yours though. I have a Lacie 2TB external as my TM back-up for my iMac, this takes care of my iPhoto library and documents. I have a Drobo thunderbolt, with dual disk redundancy for my primary iTunes storage (running at about 5TB...lots of ripped DVD's and home movies), this is then backed-up using Carbon Copy Cloner to another Drobo, with single disk redundancy. For off-site I use an 8TB G-RAID with thunderbolt which clones both the iMac and the Drobo using CCC, but I only bring it back home about once per month, update it and then take it back to the office and stick it in a drawer. My iTunes and home movie library doesn't change that often. Finally, I use Crashplan for my iPhoto, documents and home movies, so if all else fails, I have the cloud! This way, I have at any one time, two onsite instances of my data, plus an offsite copy, plus a cloud copy for critical data I would not want to lose! Probably paranoid, but I sleep better at night!

I like the idea of the bootable clone however, and I don't have one of those. The TM doesn't as you know, and any RAID will not support a bootable clone using CCC. What I need is another single drive for the iMac. Given I have recently swapped out bare 2TB drives on my Drobo's for 4TB's, I really like your idea of the drive dock, I could use that for my bootable copy! So thanks very much and keep up the good work!