Symptoms

The following errors can appear when performing a VSS-aware backup:


  1. VSS: The writer failed due to an error that might not occur if another snapshot is created(Dhcp Jet Writer)(Specific GetWriterStatus)(Snapshot continued)     
    • warning: VSS: Retry performing snapshot since a RETRYABLE error was encountered performing last snapshot. (Dhcp Jet Writer)
  2. VSS: The writer failed due to an error that most likely would occur if another snapshot is created(MSDEWriter)(Specific GetWriterStatus)(Snapshot continued)
  3. VSS: The writer failed due to an error that most likely would occur if another snapshot is created(NTDS)(Specific GetWriterStatus)(Snapshot continued) "
  4. VSS: The writer failed due to an error that might not occur if another snapshot is created(Microsoft Exchange Writer)(Specific GetWriterStatus) 
    • Warning: The process cannot access the file because it is being used by another process. (\\ServerName\C$\ProgramFiles\Microsoft\Exchange Server\V15\Mailbox\Mailbox Database\Mailbox Database.edb)

 

Cause

The causes of these errors are as follows:

  1. This error can occur due to a difference in timing between the start time of a backup that is regularly run by DHCP and that of the backup software that uses the Volume Shadow Copy service. The error might be reported if the VSS backup that is triggered by Asigra overlapped with the DHCP database backup. The default backup path of the DHCP database is:  %systemroot%\System32\Dhcp\    
    • This error can occur if the VSSControl.exe received a RETRYABLE error from a VSS writer when creating a snapshot. The DS-Client will retry the backup until the maximum retry count for creating snapshot is reached. The maximum retry count is configurable in DS User (Setup > Configuration > Advanced > Miscellaneous).
  2.  This error can occur when the SQL Writer needs to be excluded in the advanced properties of the backup set.
  3.  This error can occur if the NTDS writer is in failed state or there are stale snapshots from previous VSS attempts.
  4.  This error can occur when attempting to restore the replica copy of Exchange DAG using the VSS option.

Solution

1. Retry the backup by the backup software, change the trigger of the backup by the backup software, or change the interval of the regular DHCP backup and cleanup.


To change the interval of the DHCP backup, edit the following registry entry.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters\BackupInterval

Note: The default value is 60 minutes and the maximum value is 71582 minutes.


To change the interval of the DHCP cleanup, edit the following registry entry.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DhcpServer\Parameters\DatabaseCleanupInterval


Note: The default value is 60 minutes and the maximum value is 71582 minutes.



The DHCP cleanup process is performed between 0:00:00 and 0:01:00 in addition to the regular cleanup. Do not set up any backup schedule during this period.


For more information, see the following Microsoft KB article:

https://support.microsoft.com/en-us/kb/3007202

  • The warning can be ignored if backup is finished successfully. However, if the backup failed, you should apply the suggested workaround as described in this Knowledge Base article


2. Exclude the MSDE writer (SQL writer) in DS-User (Sets > Backup Sets > Properties> Advanced Options > Exclude some writers / components) and then perform the backup again.

3. Run: vssadmin list writers to confirm the NTDS writer state, re-register the dll files and reboot the server to fix the NTDS writers

regsvr32 <="" em="">(ntdll.dll)


Run: (vssadmin list shadows) to confirm the existence of snapshots and then run (vssadmin delete *) to delete the snapshots.

4. The replica copy can only be restored using the File Restore option.