As long as only one OS is accessing the drive, I'd create just one partition. For Windows, it would be NTFS.
I would then use Acronis TrueImage to make full-disk backups.
In fact, that's exactly what I'm doing today, except that the backup drives are only 500 GB for the moment.
With this arrangement, you can be up and running again in under an hour after a disk failure, once you've installed the replacement disk.