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Should I shrink DataSources which have over 100GB unused space, should I worry about free space fragmentation and increased extents? RRS feed

  • Question

  • Hi,

     

    We have a newly setup DPM 2010 system with about 18TB of backup to disk space RAID 10 SAN space.

     

    After a couple of weeks we only appeared to have 1TB unallocated. After a bit of investigation it appeared we had a lot of space reserved for backups which didn’t really need to be that big.

     

    I’ve written a PowerShell script to keep an eye on the system and report on data sources which have over 100GB unused

     

    http://gallery.technet.microsoft.com/ScriptCenter/en-us/ef6fcd50-d280-473b-a348-149d1cc77860

     

    We appear to have well over 100GB Shadow Copy or Replica unused space for a lot of our server infrastructure and I’m considering shrink them down.

     

    I read following article http://blogs.technet.com/b/dpm/archive/2010/03/31/how-much-can-i-shrink-recovery-point-volumes-with-dpm2010.aspx which says “Repeated small shrinks cause free space fragmentation and increases the number of extents

     

    As were talking RAID 10 do I need to worry about free space fragmentation and if I’m sure we have over committed space in DPM should I go ahead and shrink them?

     

    I’m new to the product so please be gentle!

     

    Kind Regards,

     

    John

    Thursday, November 4, 2010 10:15 AM

Answers

  • Hi,

     

    As long as you have the desired number of recovery points and DPM is deleting expired RP's daily now, then it's safe to shrink the RP volumes, the shrink option in DPM will calculate the amount to shrink and do that for you.   We don't recommend or support shrinking the replica volume because there is a possibility of loosing recovery points.  If you do decide to take the chance, shrink the replica first - then the recovery point volume.

     

    The fragmentation we're talking about is on the dynamic disk, where you end up having a bunch of small slivers of free space and that causes new volumes  or extending exisitng volumes to be fragmented.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Friday, November 5, 2010 2:03 AM
    Moderator

All replies

  • Hi,

     

    As long as you have the desired number of recovery points and DPM is deleting expired RP's daily now, then it's safe to shrink the RP volumes, the shrink option in DPM will calculate the amount to shrink and do that for you.   We don't recommend or support shrinking the replica volume because there is a possibility of loosing recovery points.  If you do decide to take the chance, shrink the replica first - then the recovery point volume.

     

    The fragmentation we're talking about is on the dynamic disk, where you end up having a bunch of small slivers of free space and that causes new volumes  or extending exisitng volumes to be fragmented.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Friday, November 5, 2010 2:03 AM
    Moderator
  • Thanks for the clarification on the Recovery Point volumes and Replica volumes, I think the majority of 'wasted' space is indeed Recovery point space.

    I think I'll monitor the usage until the points expire. as it would be nice to make sure DPM takes care of it ;o)

    Thanks again it's a great help

    J

     

    Saturday, November 6, 2010 9:15 AM
  • Hello,

     

    do you have a script that will free unused space (like autoshrink) of Recovery point space?

    Friday, June 24, 2011 1:47 PM
  • Hi,

    You can download this DPM powershell script shrink-diskpart.zip file from the following location.  This may be updated at a later time and is supplied as-is, use at your own risk.

    https://skydrive.live.com/redir.aspx?cid=885774776d4f197a&resid=885774776D4F197A!120

    It has three modes of operation and will prompt to select one during execution.

    R = Report, S = Shrink with confirmation, A = Automatically Shrink all possible volumes:


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Friday, June 24, 2011 2:41 PM
    Moderator