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Online Defrag taking too long? RRS feed

  • Question

  • Hi All,

    How long would you expect an online defrag to take on a 120gb database?  We are seeing it take more than 6 hours which means that the backups kick in and kill the process, would be interesting to hear your views.

    Stewart

    Wednesday, August 25, 2010 1:07 PM

Answers

  • Stewart,

    Several of these messsages taken together give the best response for your question.  You have already expanded your online maintenance window as much as you can during the week, but as Andy said, expand your window on the weekend so it takes the full time.  You may also skip backups on weekends to ensure you complete the online defrag.  At this point, getting the online defrag to complete should be more important for you than getting a backup to complete on a lax day.  If the defrag doesn't complete over a period of several weeks, you could end up with a corrupt database - I've seen this happen, and it's not pretty.

    Additionally, if you take Elvis' advice, you'll figure if your defrag is pausing.  Remember, it will pick up where it left off, and not try to start over at the beginning, so patience will serve you well.

    Finally, I'd suggest you split the DB into two separate DBs (BOTH NEW DBs) and decommission the old one, if possible.  This should allow your system to complete the defrag more readily than it is able to now.

    HTH, and good luck.

    • Marked as answer by ssssstew Monday, August 30, 2010 12:06 AM
    Thursday, August 26, 2010 12:39 PM

All replies

  • Since it's 120 GB it will take time.

     

    -bpara

    Wednesday, August 25, 2010 1:18 PM
  • Why the need to do an offline defrag?

     

    Wednesday, August 25, 2010 1:27 PM
  • How many mailboxes are there in this DB.

    It will take long time to do online defragmentation.

    Check your eventlog for event id 1221 and determine whether to go for a offline defrag.

    Better to hold of the backup schedule a bit for one day and then wait for the complete online defrag time to complete.

     

    thanks

    Thiyagu


    Thiyagu | MCTS/MCITP - Exchange 2007 | MCSE 2003[Messaging] | http://www.myExchangeWorld.com. This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, August 25, 2010 2:29 PM
  • @andyD - its an online im trying to do using the Maintenance Period.

    Theres probably about 150 MBs in the DB.

    I think these not completing are also causing us event 1173 errors.

    Doesnt look like they ever complete through a day, so not sure how to troubleshoot that?

    Maybe just turn off the online defrag?

    Thursday, August 26, 2010 1:20 AM
  • Ah gotcha. No, do not disable the online defrag.

    What hours is it set to now?

    Can you set it to run longer  on the weekends?

    Thursday, August 26, 2010 1:30 AM
  • im currently trying to tweek backup windows to try and give it maximum amount of time to run.

    Ive just changed the maintenance interval so that it gets from 5pm to 6am every day to get as much time as possible to run, and enabled minimum logging as per

    http://blogs.msdn.com/b/jeremyk/archive/2004/06/12/154283.aspx

     

    Thursday, August 26, 2010 2:14 AM
  • Do know about you but if you want to shrink the database I would probably create another db and move the mailboxes.
    Thursday, August 26, 2010 4:44 AM
  • Hi,

     

    Have you find 70X event in the event log?

     

    If the time for the online maintenance can’t be finished one time, the next time for online maintenance, the process resumed the processing, and then eventually finished successfully (event 702 and 703). If it finishes during this time online maintenance window, it will begins with a new online defragmentation for this time of a full pass (event 700).

     

    If the time period for the online maintenance is not enough, the online maintenance should be finish several times. After we got 703 that the online maintenance has been terminated, the next time when the online maintenance begins, it consumes the processing of the online maintenance, and then finish the online maintenance. We can see it finished successfully from 703 event entry.

     

    Hope this helps. Thanks,

     

    Elvis

    Thursday, August 26, 2010 8:30 AM
  • Hi,

    Exchange database online defragmentation occurs automatically as part of the database maintenance process. Online defragmentation detects and removes database objects that are no longer being used. The online defragmentation process provides more database space without changing the file size of the database. By default, Exchange is configured to run online defragmentation daily between 01:00 and 05:00.

    To increase the efficiency of maintenance and backup processes, you may want to schedule your maintenance processes and backup operations to run at different times.

    Offline defragmentation taking 9 GB per hour is the speed at which the Eseutil utility runs. This number is only for reference. The exact number depends on your hardware and production environment.

    One option for database defragmentation create a new storage group move all user from old storage group to new Storage group and vise versa, same activity perform all the storage group, it will clear the whitespace of the database.


    Dinesh
    Thursday, August 26, 2010 10:54 AM
  • Stewart,

    Several of these messsages taken together give the best response for your question.  You have already expanded your online maintenance window as much as you can during the week, but as Andy said, expand your window on the weekend so it takes the full time.  You may also skip backups on weekends to ensure you complete the online defrag.  At this point, getting the online defrag to complete should be more important for you than getting a backup to complete on a lax day.  If the defrag doesn't complete over a period of several weeks, you could end up with a corrupt database - I've seen this happen, and it's not pretty.

    Additionally, if you take Elvis' advice, you'll figure if your defrag is pausing.  Remember, it will pick up where it left off, and not try to start over at the beginning, so patience will serve you well.

    Finally, I'd suggest you split the DB into two separate DBs (BOTH NEW DBs) and decommission the old one, if possible.  This should allow your system to complete the defrag more readily than it is able to now.

    HTH, and good luck.

    • Marked as answer by ssssstew Monday, August 30, 2010 12:06 AM
    Thursday, August 26, 2010 12:39 PM
  • Thanks everyone for their comments on this thread.

    I extened the maintenance interval out to the whole weekend and also disabled the mailbox backups over this time period (which i think i will do all the time now) and am pleased to report that the online defrag has completed :)

    Monday, August 30, 2010 12:06 AM