Druva already something similar called Cloud Cache. 
Excerpt: Metadata is managed directly on the cloud for snapshot consistency and global
deduplication across all enterprise endpoints.<p><a href="http:&#x2F;&#x2F;www.druva.com&#x2F;documents&#x2F;Druva-CloudCache-Datasheet.pdf" rel="nofollow">http:&#x2F;&#x2F;www.druva.com&#x2F;documents&#x2F;Druva-CloudCache-Datasheet.pd...</a>