If you need one unprotected drive, then I’d just carry a USB 3.0 drive and be done. More portable than the Mini, with exactly the protection (none) you seek.
yes drobo is quite good as it works with 1 drive, (giving you just under half the drives capacity as usuable)
(single drive mode wont protect you if that whole hard drive fails, but at least your data is in 2 places in case of some bad sectors)
quick tip with usb drives (usually flash sticks):
eg: if you are taking a usb stick with some large files like your vid files above etc and dont want to have to take your drobo with you.
use quickpar to make a few small protection blocks for that file
copy the file to usb (along with the extra block file/s)
& take the quickpar install file with you (if your laptop doesnt already have it etc)
if you encounter a read problem with the files on the memory stick, simply copy them to a hard drive and then use quickpar to read what it can from the file, and reconstruct the missing/damage bits using those block files.
this just takes a bit of time to prepare for, but can usually be done while you make a coffee or something
and can help to better ensure that you can access your data on a road trip, instead of shouting at the flash drive and being miles away and unable to access it