Windows 2012 system state backup with huge recovery point volumes RRS feed

  • Question

  • Apologies if this question has already been asked, but i have an issue where certain windows 2012 protected servers are taking up huge amounts of disk space in DPM. 

    One example is a server with an approx 40GB C:, system state and BMR backup. I have checked in the windows backup logs and each backup is reporting as approx 40GB in size, and we have the retention set on the protection group to 30 days. The replica vol is using 42.73GB, but the recovery point vol is use 1149.04GB.

    It appears to me as if DPM is unable to recognise the block level changes and so is storing the full 40GB for each of the 30 days. Strange thing is we are not seeing this on other Windows 2012 servers...

    Any thoughts on how to proceed?


    Friday, January 3, 2014 4:47 PM


  • Hi,

    DPM does not control what gets written to the replica volume when performing BMR backups. Windows server backup is invoked on the protected server and Windows server backup writes the BMR backup files directly to the DPM replica volume via a network share.  Therefore there is no block level tracking that can be done by DPM on the protected server for BMR backups.

    DPM also does not control what is written to the recovery point volume (ever). In the case of BMR backup, when the Windows backup BMR file is overwriten on the Replica volume, Windows shadow copy (VSS) performs a copy-on-write (COW) for blocks that are different between the last backup and the one being written.  So basically the recovery point volume should only contain delta changes.  It seems something may be running on that particular server that is skewing the output of the BMR backup so that a majority of the blocks being overwritten are not the same as the blocks of the previous backup, so more COW is occuring and resulting in larger deltas and thus requiring more space on the recovery point volume.

    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

    Friday, January 3, 2014 9:15 PM