As an Avamar beginner I had an issue with support personnel continuing to send me data to be imported into Avamar in the wrong format on NAS (must be VHD, USB drive, or ISCSI share) after explicitly explaining the formats data must be shipped in.  Since Avamar will only see data on a physical volume and not network drive I found a way to resolve this issue. You can create symbolic link on a server pointed to the network share and Avamar will see it to import the data....hope this helps someone else.

http://serverfault.com/questions/108193/mount-network-drive-as-physical-drive