Database Backup Drive Occupancy
You have options 


Move away the backup files to a network share or a central backup server. Based on your company's retention policy, the backup can be archived to tape or just deleted (Caution !). This way if you lost the backup drive, you still have backups.
For VLDBs, you have to look into a good workable (meeting your company's RTOsand RPOs) backup (and restore) strategy.


E.g. Take weekly full backup, daily diff and transaction log backups say 15mins... This way, you wont end up taking FULL backups. You can be creative to check - how much database has changed since the last full backup before taking a diff backup.



The take away is to do proper storage planning. Enable Instant file initialization and yes do test your restores ... since a backup is no good unless you can restore it !