Re: Backups?
Commvault will cheerfully do a live VM image and backup, both full backup and incremental. If the underlying storage supports it, they have a feature called "Intellisnap" that leverages the storage's snapshot feature to take the image, although it's slightly more convoluted.
(I don't work for commvault, but I do use their product at my company.)
As for size: yeah, disk to disk, then secondary copy (aux. copy in commvault's parlance) to tape.