When attempting an Exchange 2013 DAG backup with Avamar 7, the backup fails with the following error:
2014-06-17 11:24:37 avexvss Info <0000>: Initializing PowerShell interface, launching impersonated process
2014-06-17 11:24:43 avexvss Error <0000>: Access to the path 'T:\TEMP\tmp_r1hl2zi1.2um' is denied.
2014-06-17 11:24:44 avexvss Error <0000>: at System.Management.Automation.Internal.PipelineProcessor.SynchronousExecuteEnumerate(Object input, Hashtable errorResults, Boolean enumerate)
at System.Management.Automation.Runspaces.LocalPipeline.InvokeHelper()
at System.Management.Automation.Runspaces.LocalPipeline.InvokeThreadProc()
2014-06-17 11:24:44 avexvss Error <16954>: Unable to initialize Powershell interface process -- cannot continue.
2014-06-17 11:24:44 avexvss Info <7753>: Exit main body...
After some investigation we came across an issue where Windows 2012 is deployed on top of vSphere 5 or above the hot plug feature causes Windows to see all the attached drives as removable. This in-turn can cause many issues, including the permission issues seen above.
In order to resolve the issue hot plug was disabled for the effected server following this VMware article: http://kb.vmware.com/kb/1012225.