I can't speak for Windows, but the setup where I work involves four drives (currently 2 TB each), with three running as a triple-mirror ZFS pool. For backup, I split a drive off the pool, pull it, slide in the previous backup, and resilver the newly-inserted drive. Each time, I use a different drive bay.

The ZFS pool itself provides backup for several other systems, and snapshots are made periodically by a cron job to provide a further line of defense.