Monday, November 14, 2011

Exchange 2010 DAG transaction logs are not truncated after VSS Full backup

A couple of months ago we implemented for a customer a hosting solution based on Exchange 2010. The solution has full redundancy for all components including a DAG with geographical redundancy.
Everything was configured accordingly to Microsoft recommendations and worked without any problems.

We configured Windows Server Backup to perform backups using a DAG member that was hosting only active databases. This means that we didn't have to do the Registry modifications as mentioned in TechNet (
The backup was successful but not logs were deleted from the log's folder. In the Event Viewer the only relevant record was:

Information Store (2672) DB1: No log files can be truncated.

Exchange VSS Writer (instance acedea2e-c785-3e33-8257-ac38405e81af:5) has successfully completed the full or incremental backup of replicated database 'DB1'. The log files will be truncated after they have been replayed.

We tried to find a solution and nothing worked and we had to give up for a while in using DAG replication. Microsoft support has extensively investigated the issue for more than two months without success. In the end their suggestion was that between the geographically dispersed members of the DAG there was something that was blocking the traffic.

We discussed with the network infrastructure admin and all the ports seems to be open. The only thing that could block the communication was a Network Intrusion Detection System. This system was blocking SUNRPC and DCERPC protocols. After we disabled this protection and run the backup, all database logs were truncated.

If you encounter this issue, try to disable everything that could potentially block the communications between DAG members.


  1. i dont have geographically dispersed members .. both the members are in LAN but still no logs are getting rid... any suggestions ...

  2. Do you run the correct backup (Vss full backup with log truncation)?
    Do you have any error in the Application Log?

  3. In your DAG Don't forget to enable Circular Log after adding all passive copy, It will be to truncate log file but you won't be able to do incremental backup, just full backup will be available