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Summary



DPX asynchronous deduplication is a feature that integrates with NetApp storage systems to enable use of NetApp Advanced Single-Instance Storage (A-SIS) deduplication for Advanced Recovery backups. Enabling asynchronous deduplication allows the backkup job to finish more quickly by handing off the A-SIS request to the NetApp storage system to run as a background process. The processing occurs after the SnapVault data transfer completes and the relevant snapshot data is cataloged on the master server. This article describe how to check if asynchronous deduplication is enabled or disabled and how to change that state.

Symptoms



The Advanced Recovery backup job report displays the following:

Waiting for A-SIS snapshot notification

The message can remain for many hours, and appears to be hung.



Resolution



If A-SIS deduplication appears to be hung, check the setting for asynchronous deduplication. Perform this check through the BEX/NSB/DPX syncui command. For information about invoking syncui, see Setting Up an Interactive Command Line Interface for SYNCUI.

Note: If the syncui interface is not used exactly as described, unrecoverable errors may result.

To Check the Status of Asynchronous Deduplication:

  1. Execute syncui in the product directory through a command line on the master server.
  2. When syncui displays the interactive command line, enter the following:

    c s <localhost>
    db login sysadmin <password>
    pref list async_asis_options

If hostname does not connect, use the IP address.

If you do not receive useful output, asynchronous duplication is not enabled. Disabled is the default.

To Set or Change the Status of Asynchronous Deduplication:

  1. Follow the instructions above to display the syncui command prompt, connect to the master server, and log in.
  2. The async_asis_options preference accepts the value Y (enabled) or N (disabled). If the preference is not set, add it by entering the following:

    pref add async_asis_options Y
    or
    pref add async_asis_options N
     
  3. If the preference is set, you can change its value by entering the following:

    pref replace async_asis_options N
    or
    pref replace async_asis_options Y
     
  4. Use the pref list async_asis_options command to confirm that your preference has been added or changed.

Effects of Asynchronous Deduplication on NetApp Snapshot Names:

The default (asynchronous duplication disabled) causes deduplication to wait until the NetApp storage system completes its A-SIS process and then renames the resulting chain of snapshots. The snapshot name starts with SSSV_, followed by the Catalogic Software Data Protection job name, and then an integer number. For example, for a backup job ServerJobA that has run three times, the following snapshot names are generated:

SSSV_ServerJobA.0
SSSV_ServerJobA.1
SSSV_ServerJobA.2

The snapshot with integer .0 is the most recent.

NOTE: The above snapshot naming convention will prevent the snapshots to be able to be IA mapped. However they will be still accessible via IA anyware.

If the async_asis_options preference is set to Y, the behavior changes. The backup job finishes sooner and hands off the A-SIS operation and snapshot name to the NetApp storage system. In this case, snapshots do not end in a series of consistent small integers. Rather, the snapshot name ends in the job ID number. For example, if the backup job ServerJobA runs three times with asynchronous deduplication enabled, snapshot names similar to the following are generated:

SSSV_ServerJobA.1277225418
SSSV_ServerJobA.1277234510
SSSV_ServerJobA.1277356781

In this case, the snapshot with the highest job ID (1277356781) is the most recent.