Our organization has a Microsoft Exchange 2010 Infrastructure comprising 4 servers.  2 Servers are CAS/HT servers in an NLB.  2 Servers are Mailbox Servers in a DAG configuration.  All running on 2008R2.

Question 1:  I have installed the Avamar Windows Client Plugin on all 4 servers and the  Exchange VSS Plugin on the 2 Mailbox Servers.  I would like to confirm that I do NOT need the Exchange VSS Plugin on the CAS/HT servers.

Question 2:  I created a Group, added all 4 Servers to the Group.  The dataset assigned to the group has the Windows File Systems, Windows VSS and Exchange VSS Plugins assigned to it.  I have the options on the Exchange VSS plugin to only backup the Passive Copies of the database.  I ran my first backup last night and the server with the Passive Copies completed successfully, but the server with the Active Copies failed.  Is this to be expected and thus the server that holds the active databases will fail every night?

2012-05-08 20:48:45 avexvss Error <0000>: No items to backup, no snapshot will be taken.

2012-05-08 20:48:45 avexvss Error <0000>: Failed to expand targets.

Question 3:  Is there any documentation that might discuss Pros and Cons of backing up/restoring when backing up the active vs. passive copies of the databases?

Thanks in Advance

Ken