My blog series on VSS backups for Exchange

https://blogs.technet.com/b/exchange/archive/2012/06/04/everything-you-need-to-know-about-exchange-backups-part-1.aspx

https://blogs.technet.com/b/exchange/archive/2012/06/14/everything-you-need-to-know-about-exchange-backups-part-2.aspx

https://blogs.technet.com/b/exchange/archive/2012/07/09/everything-you-need-to-know-about-exchange-backups-part-3.aspx