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Secondary DPM server daily jobs transferring very large amounts of data from primary dpm RRS feed

  • Question

  • We recently installed a secondary DPM server offsite to backup our primary dpm server.  The initial sync was done on the lan, and then the server was moved to the remote location.

    The server has been in place for 2 days now, and jobs are taking much too long.  I have several jobs that have transferred 20-25GB of data so far, and those are still running.  The jobs in question are mostly system protection, and the servers listed are all backed up with BMR on dpm1.  

    As I understand it, DPM2 should be doing an express full backup, so there's no way that it should be transferring that much data from DPM1.  What could be wrong here that would cause this much data to be resynchronized?

    Thursday, March 31, 2011 9:09 PM

Answers

  • For anyone who happens to come across this thread looking for an answer, I did get an answer in another thread on a mostly unrelated topic. This was posted by Mike Jacquet:

    "As far as BMR is concerned, the reason why the secondary DPM server seems to replicate the whole BMR image each time is due to the way BMR is performed on the Primary. Windows Server backup on the protected server "overwrites" the entire BMR backup image .vhd file(s) on the DPM server, so the DPM Filter tracks those overwrites and the secondary needs to bring them over and apply the writes to it's copy, basically overwriting the entire image vhd file(s).   So we are only bringing over changed blocks, but every block has changed due to the overwrite method of BMR backups."

     

    Effectively, this is considered working as intented, and not a bug in DPM.  As such, it has not been addressed at all in DPM 2012 and will continue to transfer the full BMR backup to the secondary dpm server every time.

    • Marked as answer by NeighborGeek Thursday, December 29, 2011 2:27 PM
    Thursday, December 29, 2011 2:27 PM

All replies

  • Looking into this further, it definitely seems to be related to BMR backups.  The daily 'system protection' jobs on DPM2 are transferring 50+GB of data from DPM1 on any server that DPM1 does a BMR of.  

    I have found a few other people reporting this problem, but I either haven't found an answer or don't understand the answers I have seen.  The following thread seems to say that each server using BMR should be changed to do incremental backups using wbadmin.msc, but still doesn't really make much sense.  I can see where incrementals would shift work from DPM1 to the server being backed up, and transfer less data to dpm1, but not transfers from DPM1 -> DPM2...

    http://social.technet.microsoft.com/Forums/en-US/dpmssandbmrbackup/thread/ebb1f884-c44b-435b-a9eb-a5f5235e6e9b

     

    I do have one  job  taking a long time and transferring large amounts of data that is not BMR/system protection, but that is a file server, and does in fact see ~20gb of changed data daily, in the form of scripted backup jobs that copy data over to that server.

    Tuesday, April 5, 2011 5:47 PM
  • Have a look at the following thread - there are some suggestions there where I've been asking the same questions. Basically dependent on how the system protection is configured depends on what DPM transfers across the wire to the secondary DPM server. I'm not impressed with this handling of the BMR data in DPM 2010 and it does really kill off-site BMR protection across a slower link.

    http://social.technet.microsoft.com/Forums/en-NZ/dpmssandbmrbackup/thread/ebb1f884-c44b-435b-a9eb-a5f5235e6e9b

    Wednesday, April 6, 2011 7:16 AM
  • Thanks danny.  Your thread is actually the same one I mentioned above.  I found it after I originally posted here, and I added a few clarifying questions to your thread, but haven't got a response.  I don't see any documentation for DPM that even suggests the secondary dpm server should transfer the entire BMR backup of a server across the WAN each day.  Our wan connection is 10MB, so I wouldn't consider it slow, but for multiple servers at 50GB or more each, that's still a lot of data to move.
    Wednesday, April 6, 2011 11:59 AM
  • For anyone who happens to come across this thread looking for an answer, I did get an answer in another thread on a mostly unrelated topic. This was posted by Mike Jacquet:

    "As far as BMR is concerned, the reason why the secondary DPM server seems to replicate the whole BMR image each time is due to the way BMR is performed on the Primary. Windows Server backup on the protected server "overwrites" the entire BMR backup image .vhd file(s) on the DPM server, so the DPM Filter tracks those overwrites and the secondary needs to bring them over and apply the writes to it's copy, basically overwriting the entire image vhd file(s).   So we are only bringing over changed blocks, but every block has changed due to the overwrite method of BMR backups."

     

    Effectively, this is considered working as intented, and not a bug in DPM.  As such, it has not been addressed at all in DPM 2012 and will continue to transfer the full BMR backup to the secondary dpm server every time.

    • Marked as answer by NeighborGeek Thursday, December 29, 2011 2:27 PM
    Thursday, December 29, 2011 2:27 PM