I recently set up a new Veeam Backup & Replication v8 demo lab, and my intial small job that consisted of two different Linux VMs and one Windows Server 2012 R2 Domain Controller was chugging along nicely. I had one minor from the start though, and that was that file indexing consistently failed for the Windows VM. No big deal, but I thought it was strange at the time. After all, the Linux VMs were indexed just fine.
Fast forward a few days, and all of a sudden Veeam B&R was unable to back up the Windows VM at all, failing with the following error:
RPC function call failed. Function name: [IsSnapshotInProgress]. Target machine: [192.168.5.5].
RPC error:Access is denied.
Nothing had changed in my environment, no patches had been installed, no changes made to the backup job or the credentials used. I even tried deleting the job, this is a demo environment after all, and re-creating it, but with the same end result.
As the Access is denied message clearly states, this had to be related to permissions somehow, but I was using domain administrator credentials (again, this is a lab), so all the required permissions should be in place, and the credentials test in the backup job also checked out just fine. It has also worked fine for 5 or 6 days, so I was a bit baffled.
In the end, I tried changing from using User Principle Name (UPN) connotation of email@example.com in the credentials for the VM, to using Down-Level Logon Name aka domain\administrator and retried the job.
According to this Veeam Community Forum thread this was also a problem in v7 and has something to do with how the Microsoft API’s work.
So, if your Veeam Backup & Replication jobs fail with access denied messages, and/or can’t index the VM files, check your credentials. They may work, but they might just be entered in the wrong format.