I’ve recently added an external hdd to my NVidia Shield, and now I’m becoming paranoid that if it goes bad, I lose all my stuff. I wasn’t worried until I started reading about others who have had it happen to them. So what’s a good backup strategy for this? As I understand it’s encrypted so - what methods are available? Is there an app that can sync the drive contents with a OneDrive account or anything, even if it’s in an encrypted backup file format of some sort?
Here's what you do.
Add two storage options. Use one of the recommended USB sticks for adoptable storage. https://nvidia.custhelp.com/app/answers/detail/a_id/4334/~/what-usb-flash-drives-are-recommended-for-shield-tv Use your external HDD as external storage and not at adoptable storage. External storage is a regular filesystem and doesn't run like adoptable storage. It's not encrypted and you'll be just fine.
The best scenario is to buy/build a NAS and just use that with some form of raid depending on how many drives you're going to use.