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Circular Logging RRS feed

  • Question

  • More of my not understanding how it all works.

    We previously turned off Exchange protection because we were desperately short of space on the server and it didn't seem like DPM was clearing out the logs when it was done creating a backup.  This was with 2007.  Now that both are on 2010 and Exchange is on a new server, we are going to enable circular logging.  I know DPM is Exchange aware and that it should remove the logs after a backup, but I'm unsure about....

    1. What constitutes a "backup."  A recovery point?  A synchronization?  A backup to tape?
    2. Is there a setting that ensures DPM will clear out Exchange logs?
    3. Is there a best practice for protecting a single exchange server so its logs don't choke the drive space?

    Thanks.

    Saturday, April 2, 2011 2:57 PM

Answers

All replies

    1. Is there a setting that ensures DPM will clear out Exchange logs?
    2. Is there a best practice for protecting a single exchange server so its logs don't choke the drive space?,

    1. I do not think there is a setting that ensures DPM will clear out the Exchange logs. Only if full backup is taken then the logs get deleted. There is a time stamp on Exchange db when the full backup was taken and which is te last committed log.

    1. Is there a best practice for protecting a single exchange server so its logs don't choke the drive space?,

    Circular logging will not generate log files ( max 4-10) as the files are commited to the DB & it is not the best practice for recovering data.

    let us take take the example.

    I am not using circular looging and backing up my DB ( everyday) - Full backup

    I have 10 gb on monday mornign and by evening i have 11gb of db and 10000 logs. after sucessful backup by logs get deleted on monday night

    tuesday i have 11 gb of db and by evening it is 12 gb + 10000 logs

    on wed afternoon  by system crashes...

    I have the db which cannot be be brought online... the db is 12.5 gb whichis of no use buti hve 5000 logs files.

    i restore the tuesday backup and let the 5000 log files commit to the tuesday full db .. it becomes 12.5 and a good db. I do not lose the data

    if it had been Circular looging I would have got 12.5 gb of db crashed on wednesday afternoon , by restoring tuesday's full backup will not make any sense as i would lose the wednesday mornigndata

    so i ahve to repair wednesday mornign db an still lose data ,( so full backing up of db does not make any sense)

    Hope it helps 

    Saturday, April 2, 2011 3:10 PM
  • Most of it went over my head, I'm sorry.  After "only if a full backup is taken then the logs get deleted" I sort of tuned out.

    My main concern is what triggers the truncation and that appears to be a Full Backup (which I have set, Epxress Full Backup at 8pm every day.)

    As to the rest, in the example I'm guessing you were illustrating that with full logging (disabled circular) you're able to recover more data than with circular enabled, but you have to be very mindful of the size of the logs.

    Frankly the idea that if one backup is missed, the email server is hosed.  The alternative is that DPM doesn't work with circular enabled so I can either back it up with DPM or not.  Is that correct?

    If I see the exchange log files start approaching a limit, can I force a Full Backup ahead of schedule?  The alternative is to shut down the stores, dismount them and clean up the logs manually.
    Saturday, April 2, 2011 4:43 PM
  • As to the rest, in the example I'm guessing you were illustrating that with full logging (disabled circular) you're able to recover more data than with circular enabled, but you have to be very mindful of the size of the logs.

    Yes... Exactly...

    Circular logging enabled .. is lik all transcation logs are committed to the database and then deleted.. it takes few seconds so you may have 4-10 logs max. DPM  will not support this..

    if this db gets corrupted you need to repair it .. and you lose some data.

    but if you have circular lgging disabled.. you get many logs ..

    this logs are real time data .. this can be committed to your yesterdays backup which was taken by DPM.

    If I see the exchange log files start approaching a limit, can I force a Full Backup ahead of schedule?  The alternative is to shut down the stores, dismount them and clean up the logs manually.

    Yes a full backup will delete all logs.. ( but your incremental /differential backup taken earlier holds no good.. you should be aware of this)

    Yes the alternative is to dismount all databases in the SG and clean the logs. ( dismounting the db commits all logs into the db and makes it  clean shutdown and remountable)

     

     

     

     

    Saturday, April 2, 2011 5:03 PM
  • Excellent thank you.

    I also just noticed that a recovery point will also remove the logs.  I'm guessing that has to do with a synchronization which happens with the recovery point (that I have set anyway.)


    Saturday, April 2, 2011 5:19 PM
  • Hello,

    DPM 2010 does not support incremental backups for a computer that is running Exchange 2010, Exchange 2007, or Exchange 2003 on which Circular Logging is enabled.
    Below are a few articles that goes over this.

    http://technet.microsoft.com/en-us/library/ff399692.aspx
    http://technet.microsoft.com/en-us/library/ff918788.aspx
    http://technet.microsoft.com/en-us/library/ff399605.aspx

    Here is a good article that covers log truncation on Exchange 2010 as well:
    http://technet.microsoft.com/en-us/library/dd876874.aspx

    Thanks
    Shane

    Monday, April 4, 2011 9:43 PM
    Moderator
  • Hi,

    DPM does not truncates the transaction logs, Exchange truncates the logs on successful Backups(Express Full and Incremental). Please note that Exchange does not truncate the logs immediately after succefull backup, for truncation the transaction logs need to meet the truncation criteria. Please refer  the document Shane pointed for log truncation (http://technet.microsoft.com/en-us/library/dd876874.aspx ).


    Nagesh[MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, April 13, 2011 3:20 PM