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Disabling Restores Using Changed Block Tracking

Changed Block Tracking (CBT) is a VMware feature that enables efficient backup of virtual machines by tracking changes and only backing up changes rather than complete virtual machines. CBT is enabled by default, and is used automatically for restoring a full virtual machine when the Restore in place and Unconditionally overwrite VM with the same name restore options are used, providing significant performance improvements.

For SnapProtect, CBT restores are only supported from streaming backups (backup copy).

  1. From the CommCell Browser, go to Client Computers.
  2. Right-click the client and select Properties.
  3. On the General tab of the Client Computer Properties dialog, click Advanced.
  4. Click the Additional Settings tab.
  5. Configure additional settings:
    • To disable CBT restores, configure the bEnableSeekOptimization additional setting:
      1. Click Add.
      2. On the Add Additional Settings dialog box, provide the following information:
        • Name: bEnableSeekOptimization

        • Category: VirtualServer

        • Type: INTEGER

        • Value: 1 (enable) or 0 (disable). Enter 0 to disable this feature.

        • The Enable checkbox should be selected.
      3. Click OK to save the additional setting.

      When this additional setting is enabled, CBT restores are performed if restored changes total 50 MB or more.

    • Optional: To change the threshold for performing CBT restores, configure the nSKDMinUnchangedSpace additional setting:
      1. Click Add.
      2. On the Add Additional Settings dialog box, provide the following information:
        • Name: nSKDMinUnchangedSpace
        • Category: VirtualServer
        • Type: STRING
        • Value: 50M (default). If the amount of unchanged disk space on the backup is less than this value, a classic restore is performed instead of a CBT restore. You can enter units as K (kilobytes), M (megabytes), or G (gigabytes). 
        • The Enable checkbox should be selected.
      3. Click OK to save the additional setting.
  6. Click OK twice more to save the advanced client properties and the client properties.