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EXCHANGE DAG 2016 : Transaction Logs are not truncated if a database copy exists through veeam backup

SMI 96 Reputation points
2020-08-14T18:20:42.763+00:00

Hello,

We have DAG with 2 physical Node Cluster. Both host has active and passive database. We are using Veeam 9.5.4 to backup the database. As per Veeam there are 2 options
Node 1 - DB1 (Active-E:Drive), DB2 (Passive-F:Drive)
Node 2 - DB1 (Passive-F:Drive) DB2 (Active-E:Drive)
(Both edb and logs are in same drive)

  1. Select DAG level backup adding drives - that backup both active active and passive database. It will increase both backup window & storage space.
  2. We can select server level backup and choose the drives. - If we select just Active Copy then exchange logs don't truncate. We have to select both active and passive Copies. It will increase both backup window time & storage space.

Any body has this issue and how resolved this? As per Veeam DOC.
I saw some posts regarding this and didn't get any final answer.

https://social.technet.microsoft.com/Forums/en-US/6c9f1b19-4dc4-4109-80d7-aff851a1bd70/dag-transaction-logs-are-not-truncated-if-a-database-copy-exists?forum=Exch2019#452d1c0f-b883-40cc-9750-4a57e6856e95

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Exchange | Exchange Server | Management
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  1. SMI 96 Reputation points
    2020-08-17T14:33:21.987+00:00

    Contacted Veeam. As per them

    From Exchange 2013/2016/2019 we have to select all disk that contains Active & Passive database drives in the backup to flush the logs properly.

    Exchange Server VSS Writer
    Earlier versions of Exchange included two VSS writers: one inside the Microsoft Exchange Information Store service (store.exe) and one inside the Microsoft Exchange Replication service (msexchangerepl.exe). Back in Exchange 2013, the VSS writer functionality previously found in the Microsoft Exchange Information Store service was moved to the Microsoft Exchange Replication service. This architecture remains the same in Exchange 2016 and Exchange 2019. This writer, named Microsoft Exchange Writer, is used by Exchange-aware VSS-based applications to back up active and passive database copies, and to restore backed up database copies. Although the writer runs in the Microsoft Exchange Replication service, it requires the Microsoft Exchange Information Store service to be running for the writer to be advertised. As a result, both services are required to back up or restore Exchange databases.

    Basically in Exchange 2010 we can get away with backing up only active copies because the Exchange writer will still be notified as it only tracks active databases. With 2016, however, the Exchange writer tracks both active and passive databases so we must include all of them for truncation to occur correctly.

    So Basically if we use Veeam to backup exchange 2016 physical servers we need to include both active and passive drives in the backup. This need more storage and backup window time. Will look in to another vendor once the veeam support maintenance end.

    Any suggestion for better backup products that take backup of active database or dag level backup that we can choose which database need to take backup.

    Thanks
    SMI

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  1. Jon Alfred Smith 541 Reputation points
    2020-08-14T19:12:13.63+00:00

    I find this very strange what you say here. Are you sure that you have configured Veeam Backup for DAG correctly. I have been working with and maintaining several Exchange organizations, with DAGs since Ex 2007 (sort of). Backup programs used: Windows Backup, Backup Exec, NetBackup and Commvault. Only used Veeam with stand-alone servers.

    Now Backup Exec, NetBackup and Commvault behave exactly the same way. You configure them to backup the DAG, which in smaller business consist of two servers, in larger three or four. The usual configuration is as at your site, a mix of active and passive mailbox databases. Most of the time these are evenly distributed, but one or more may failover before the backup job runs.

    The backup programs will check where the active databases are located and backup only them, not the passive copies. After a full or incremental backup, logs will truncate on the active database and then be replicated to the passive database(s). This is not a function built into the backup application, but a mechanism in Exchange. There's a threshold, I think about 100 MB, before log truncation is triggered. Exchange will also make sure that enough log files remain in order to restore the database.

    I cannot see that your link confirms your findings. Not sure, but there must be some Veeam documentation that guides you step-by-step through the configuration. Note: Copy or differential backups will not delete log files. Take a look here (Tony Redmond on these issues, one of the great Exchange authorities:

    https://thoughtsofanidlemind.com/2013/03/15/exchange-2013-log-truncation/

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  2. AnandN 1 Reputation point
    2021-07-13T14:56:33.317+00:00

    I must agree with SMI-7113
    After testing,
    Exchange logs are not truncated after a successful Veaam full backup with application processing and log truncation enabled.
    I tried to backup the database's copies (active and passive) on all exchange servers to see if this would but no log truncation.
    I tried to backup a database that is not part of the DAG but still no log truncation by Exchange.
    Exchange seems to not know that a successful backup was done by Veaam so it does not do any truncation.
    Never have I used or known of any backup program that requires backing up all copies of a database in order to have a full backup with log truncation. That is impractical.
    Even Windows native server backup is able to backup a Single database on a single server in a DAG and that does a full backup with log truncation fine, everytime.
    If someone is looking at Veaam to replace their existing backup solution for Exchange I suggest they really test Veamm first, because apparently its not integrated for Exchange backup. Or like the OP. look into another product.

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