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  • Question

  • In real world scenarios do may of you enable circular logging? I have never had to replay log files and usually enable circular logging.

    Also in a DAG do the transaction logs get created on each member if circular logging is disabled?

    finally what is best practice for backing up databases in a dag if i have 2 active with split mounted copies of each database so db 1,2,3 are on server one with passive 4,5 and 123, are passive on server 2 with 4,5 active then I have server 3 with 1,2,3,4,5 all passive where do I back up from?


    ***Don't forget to mark helpful or answer***

    Monday, January 19, 2015 3:57 PM

Answers

  • I wouldn't enable the circular logging and let my Daily Backup take care of log truncation. However you can enable the circular logging, it all depends on how you want to design your infra, backup and recovery strategy...

    Yes in DAG, transaction logs are copied over to other server where database copy is located, inspected and checked that it is not needed by other database before it got truncated due to circular logging. 

    I would take backup from the server 3 where all the DBs are not mounted...

    Some references:

    Circular Logging and Mailbox Database Copies - http://blogs.technet.com/b/scottschnoll/archive/2011/06/27/circular-logging-and-mailbox-database-copies.aspx

    Managing mailbox database copies - http://technet.microsoft.com/en-us/library/dd335158(v=exchg.150).aspx


    Amit Tank | Exchange - MVP | Blog: exchangeshare.wordpress.com 

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Monday, January 19, 2015 4:31 PM
  • Hi,

    Agree with Amit. Without a complete set of transaction log files, you cannot recover any data more recent than the last full backup. Therefore, in a normal production environment, circular logging is not recommended. However, this is up to your requirements.

    Because passive node is not operational and this won't affect production users, you can choose the passive node firstly.

    Best regards,


    Belinda Ma
    TechNet Community Support

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Tuesday, January 20, 2015 6:21 AM
  • Hi ,

    If you are using the exchange aware backup software then that doesn't a matter of on which server you are running the exchange full back up.

    Say for instance you are running exchange full backup on server 3 .Once the backup gets completed transaction logs will get purged on all the three servers.


    Thanks & Regards S.Nithyanandham

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Tuesday, January 20, 2015 2:24 PM
  • Thanks Both, so do I enable circular logging on the passive nodes?
    Scenario:

    if DB A has logging enabled on Server 1 copy and generates a 1MB log file

    If passive copy of DB A on Server 2 has logging enabled does it also store/copy the 1mb log file on disk

    Daily backup runs and truncates the 1MB log file on Server 1 does it remove it from server 2 also?

    Or do passive nodes use circular logging by default?


    ***Don't forget to mark helpful or answer***

    Circular logging applies to the database, not whether its active or passive. If you enable it, it applies to all the copies of that database.


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Tuesday, January 20, 2015 3:08 PM

All replies

  • I wouldn't enable the circular logging and let my Daily Backup take care of log truncation. However you can enable the circular logging, it all depends on how you want to design your infra, backup and recovery strategy...

    Yes in DAG, transaction logs are copied over to other server where database copy is located, inspected and checked that it is not needed by other database before it got truncated due to circular logging. 

    I would take backup from the server 3 where all the DBs are not mounted...

    Some references:

    Circular Logging and Mailbox Database Copies - http://blogs.technet.com/b/scottschnoll/archive/2011/06/27/circular-logging-and-mailbox-database-copies.aspx

    Managing mailbox database copies - http://technet.microsoft.com/en-us/library/dd335158(v=exchg.150).aspx


    Amit Tank | Exchange - MVP | Blog: exchangeshare.wordpress.com 

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Monday, January 19, 2015 4:31 PM
  • Hi,

    Agree with Amit. Without a complete set of transaction log files, you cannot recover any data more recent than the last full backup. Therefore, in a normal production environment, circular logging is not recommended. However, this is up to your requirements.

    Because passive node is not operational and this won't affect production users, you can choose the passive node firstly.

    Best regards,


    Belinda Ma
    TechNet Community Support

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Tuesday, January 20, 2015 6:21 AM
  • Thanks Both, so do I enable circular logging on the passive nodes?
    Scenario:

    if DB A has logging enabled on Server 1 copy and generates a 1MB log file

    If passive copy of DB A on Server 2 has logging enabled does it also store/copy the 1mb log file on disk

    Daily backup runs and truncates the 1MB log file on Server 1 does it remove it from server 2 also?

    Or do passive nodes use circular logging by default?


    ***Don't forget to mark helpful or answer***

    Tuesday, January 20, 2015 8:23 AM
  • Hi ,

    If you are using the exchange aware backup software then that doesn't a matter of on which server you are running the exchange full back up.

    Say for instance you are running exchange full backup on server 3 .Once the backup gets completed transaction logs will get purged on all the three servers.


    Thanks & Regards S.Nithyanandham

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Tuesday, January 20, 2015 2:24 PM
  • Thanks Both, so do I enable circular logging on the passive nodes?
    Scenario:

    if DB A has logging enabled on Server 1 copy and generates a 1MB log file

    If passive copy of DB A on Server 2 has logging enabled does it also store/copy the 1mb log file on disk

    Daily backup runs and truncates the 1MB log file on Server 1 does it remove it from server 2 also?

    Or do passive nodes use circular logging by default?


    ***Don't forget to mark helpful or answer***

    Circular logging applies to the database, not whether its active or passive. If you enable it, it applies to all the copies of that database.


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    • Proposed as answer by Belinda Ma Monday, February 2, 2015 3:09 AM
    • Marked as answer by Belinda Ma Tuesday, February 3, 2015 2:41 AM
    Tuesday, January 20, 2015 3:08 PM