Kindly find below steps.

1. Login to the Admin GUI console of the below Avamar server

2. Go to Tools -> Manage dataset  Select AllFileSytem Dataset  Click Edit  Go to Options tab  Select Windows File system Plugin  Click on More  Add the Below Parameter.

3. In the enter Attribute type:

         no-query-vols

4. In the Attribute Value type:

                A:\

5. Click ok

or go through the https://support.emc.com/kb/486961  article.