Far more disk space needed than was planned. What's going on? RRS feed

  • Question

  • Among other things we're backing up a SQL server with DPM and we're having trouble making sense of what it's doing.  Consider our largest database which has run our storage pool disk out of space.  The size of the database is almost 60 GB (over 60 if you count it's ldf file).  Our backups for that database alone are configure as follows:

    Current Data size 59.43 GB
    Current Replica Volume 270.85 GB
    Current Recovery Point Volume 502.8 GB
    Short-term protection using disk (no tapes)
    4 days' retention, sync every 15 minutes with full backup daily at 8PM

    With 4 day's retention and synchs every 15 minutes, DPM has 406 Recovery Points for this database before it ran us out of space.  Our understanding was that incremental backups were run every 15 minutes, which was just CHANGES.  Is it actually running differentials?  What is the difference between the Replica Volume and the Recovery Point Volume?  What explains why it's so much bigger?  One of the difficulties we're having when we use DPM is estimating how much disk space we're likely to use for a given configuration (Some kind of feature that can estimate disk usage that might be nice, and yes, I understand anything that would do that would be missing useful information about the data utilization).

    Even though this is a database and that muddies the waters a bit we're seeing similar but not as pronounced disk consumption for items in other Protection Groups.  Is there documentation I missed about how DPM uses it's storage pool?

    Monday, November 22, 2010 8:15 PM


All replies

  • Hi,

    I'm a a relative newbie to DPM but it's my "limited" understanding that

    A Replica Volume is a copy of the data benig backed up and is syncronised/updated with no previous version (I think of this as a DR copy - previous versions aren't availble)

    A Recovery point is a VSS snaphot/previous version or increment backup (I think of this more as of a traditional increment backup you use to rest data from a previous version)

    You'll find the the sapce is "allocated" and not "used" ;o) So it may be that the system has overallocated space.

    How big is the disk that host the database ... is it near 270GB? I seem to remember something about a replica storing empty space but that my be for Hyper-V vhd backups

    Also how big are recovery points on average?

    One other point .. It was my understanding that you can't have more than 64 recovery points are you sure you have 406?

    Kind Regards,


    • Edited by John Grenfell Thursday, November 25, 2010 10:04 AM added 64 recvoery point limited
    Thursday, November 25, 2010 9:56 AM
  • [quote]Consider our largest database which has run our storage pool disk out of space.[/quote]

    How I understand it, you are complaining about DPM grabbing too much disk space, not DPM running out of Replica / Current Recvery Volume?

    In this case, the KB2250444 (from last week) might help.



    Thursday, November 25, 2010 10:08 AM
  • DPM runs a powershell script nightly which purges expired recovery points.  However, if there's some issue with your DNS or AD environment, sometimes this script cannot run.  You can run it manually from the DPM Management Shell.  It's called PRUNESHADOWCOPIES.PS1 so just google it for the correct usage.

    I had an environment where for some reason when executing this script, it said the DPM server wasn't correctly registered in AD (which it was, as all other domain functions worked as they should).  This caused the volumes to just fill with expired recovery points and I had to dig around for a script to remove all recovery points older than X days.

    Friday, November 26, 2010 5:22 PM
  • Hi Smagill

                to know how DPM allocating space and so to get an clear view in order to design a well known capacity planning for DPM Space allocating you can refer to this link to know how DPM Allocating Space for Protection Groups also there is some storage calculators for difference applications (Exchange - sharepoint - HyperV and also SQL) on this link

    *the sharepoint calculator can be used to determine the SQL storage space required also.

    addition DPM 2010 has an extra feature that make you able to let DPM Protection group allocated space grow up automatically.

    Links here:



    Thursday, December 2, 2010 5:11 PM