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Windows Server Backup error code 2155348147 with Eventid 546 caused by Bitlocker at a Hyper-V Server 2012 R2

Windows Server Backup error code 2155348147 with Eventid 546 caused by Bitlocker at a Hyper-V Server 2012 R2

Windows Server Backup error code 2155348147 with Eventid 546 caused by Bitlocker at a Hyper-V Server 2012 R2

We found a problem at one of our small customers where we run a Hyper-V Server 2012 R2 with an external backup HDD that is using Bitlocker encryption with enabled auto unlock (TPM secured).The backup should be executed through Windows Server Backup, but after the backup HDD was encrypted with Bitlocker, the Backup wouldn’t run anymore.Windows Backup showed only the following error:

Backup failed. Backup not started. The backup operation of the volume did not start.

At the eventlog, we found the following error:

The backup operation attempted at ‘‎2015‎-‎02‎-‎23T02:00:16.965013600Z’ has failed to start, error code ‘2155348147’ (The backup destination is not accessible because it is locked by Bitlocker Drive Encryption.). Please review the event details for a solution, and then rerun the backup operation once the issue is resolved.

At first we proved that auto-unlock is really enabled, the command therefor is: Get-BitLockerVolume
The output has to be: AutoUnlock True

After some research we figured out that the server did not notice that the Bitlocker HDD had been auto-unlocked because it was auto-unlockend and we have been able to access the file system of the external HDD.

And now, believe it or not: Just after that access of the filesystem, the backup was successful.

We won’t make major cost in this small customers environment, so we decided to create a dirty workaround:

  1. Open Task Scheduler
  2. Create a new basic task
  3. The task should start everyday 5 minutes before the Backup starts
  4. Action: “Start a program”
  5. Program: “cmd”
  6. Arguments: “/c dir e: /s > e:\dir.txt” (E: should be your auto-unlocked HDD)

That was it. After that, every day the backup worked like a charm, reboots included.