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Losical disk manager database occupancy reach its threshold RRS feed

  • Question

  • Dynamic disks use a private region of the disk to maintain a Logical Disk Manager (LDM) database. The LDM database is currently at 85% occupancy. When occupancy reaches 90%, all volume creations and grows will be disabled and backups that require volume grows may fail. (ID 32062)

    Need to know

    Friday, June 28, 2013 10:26 PM

Answers

  • Hi,

    The LDM database does have limitations, so our guidelines for the 300 data sources is based on those limitations.  However, Windows does support more than 600 volumes, in fact, it can actually host greater than 2500 simple dynamic volumes.  The problem comes in when DPM starts extending the replica and recovery point volumes due to poor pre-planning of space requirenents for the various data sources under protection.  If DPM extends them too many times, you bump into a hard limitation where you cannot add new volumes or extend exisiting volumes.

    To overcome that limitation once it's reached, you can identify which data source volumes have the most extents, then migrate the data source to DPM Custom volumes on BASIC DISKS using the MigrateDatasourceDataFromDPM.ps1 power shell command.  You must use the syntax to migrate a single datasource to a pair of custom volumes so no new LDM records are  required or consumed.

    Using MigrateDatasourceDataFromDPM: http://technet.microsoft.com/en-us/library/dd282970.aspx

    How to Use The Migratedatasourcedatafromdpm.Ps1 DPM Powershell Script to Move Data: http://blogs.technet.com/b/askcore/archive/2009/06/22/how-to-use-the-migratedatasourcedatafromdpm-ps1-dpm-powershell-script-to-move-data.aspx

    What volume to migrate first?: http://blogs.technet.com/b/dpm/archive/2010/03/30/what-volume-to-migrate-first.aspx

    Once you migrate it, wait for the recovery points to expire and those dynamic volumes will be deleted by DPM and free up some records in the LDM database.  Do that for the data sources containing the most extents so to free up the most LDM records.  Then once you see that those volumes have been deleted (after the recovery points expire) , add one more dynamic disk, and migrate the data sources on the custom volumes back to the new dynamic disk that has all free space, that will ensure only two records are used, one for the replica and one for the recovery point volume.   Then you can start migrating other datasources with lots of extents to the new dynamic disk and free up even more records.  Over time, you can manage to get most of your volumes back into contiguous space by migrating data sources between disks that have the most contiguous free space and reduce your LDM record count even further.  The important thing to remember is you can only migrate a data source one time until the old volumes get deleted after the recovery points expire, so depending on the retention range you have this could take days, weeks or months.

    I guess the take away is to do your storage planning up front so DPM does not need to keep growing volumes, because each time it does, it uses more LDM records which have a finite number.

     


    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.

    Saturday, June 29, 2013 3:35 PM
    Moderator