Performance of Query and Insertion (QI) of the DDB is Slow

Article ID: DD0004 Data protection jobs using Deduplication are taking longer than usual/expected.


The performance of the Query and Insertion (QI) of the DDB is slow during backups.


The slow performance of QI time indicates that the DDB is highly loaded or on a sub-optimal disk or MediaAgent.

If the QI of the DDB is suboptimal or reaching or exceeding the threshold limit (two milliseconds), the following effects might take place:

  • Disk pruning might be delayed resulting in low space
  • Deduplication ratio (% of the deduplication data) might go low
  • Performance degradation during backups

You can view the QI performance and threshold limit of the DDB from the Deduplication Database summary or DDB Partition summary. For more information, see Monitoring Deduplication Database or Monitoring Deduplication Database Partition.


Make sure that your DDB is hosted on the recommended configuration referenced in Deduplication Building Block Guide. If DDB is hosted on the recommended configuration and the QI performance is still slow, then verify and perform the following:

  • Make sure that there is no anti-virus software running on the DDB MediaAgent.
  • If DDB backups are scheduled to run very often, make sure to reduce the frequency of the schedule.
  • If VSS Snap is configured on the same DDB volume, make sure to configure on a different hard disk compared to the DDB volume. This will improve performance of the QI during the DDB backups.
  • Move Operating System Paging file on the DDB MediaAgent to a faster disk.
  • For RAID disks, enable Disk Controller caching.
  • Verify the number of VSS shadows on the DDB volume by running the following command:

    vssadmin list shadows /For= DDB Volume

    DDB Volume - is the actual volume drive letter (for example D:\) where the DDB is configured.

    If there are no DDB backup jobs running and you do not have any third party software's installed on the DDB MediaAgent that is creating and using shadows, delete any existing VSS shadows on the DDB volume by using the following command:

    vssadmin delete shadows /For= DDB Volume