Configuring Multiple Streams for Synthetic Full Backups

By default, synthetic full backups use single streams to transfer data. However, you can change the default behavior and configure multiple streams for synthetic full backups.

You can also create a schedule policy for synthetic full backups with multiple streams. For more information, see Creating a Schedule Policy for Synthetic Full Backups with Multiple Streams.

Note: Configuring multiple streams for synthetic full backups is currently supported on File System and Virtual Server Agent with Indexing Version 2. For clients that are newly created, you must first perform a backup to establish the Indexing Version 2, and then configure multiple streams for synthetic full backups. For more information on Indexing Version 2, see Indexing Version 2.


  1. From the CommCell Console, expand Client Computers > client > File System > BackupSet.
  2. Right click subclient > Backup.

    The Backup Options dialog box appears.

  3. Under Select Backup Type, select Synthetic Full.
  4. Click Advanced.

    The Advanced Backup Options dialog box appears.

  5. On the Data tab, select Use Multiple Streams.
    1. If you want to define the number of streams, select the Number of Streams option and then enter the number.
    2. Select the Allow Maximum option if you want to use the maximum number of streams, which is equal to the total number of streams used by subclients in the last cycle.

      Note: In order to optimize the performance of a synthetic full backup job, Commvault has internal logic for determining the actual number of streams for a given synthetic full job, even if you select the Allow Maximum option.

      When a synthetic full backup job starts, Commvault limits the number of streams to twice that of the data reader number used to run the backup job (subclient > Properties > Advanced > Performance > Number of Data Readers). Therefore, if the number of data readers is set to 4, the maximum number of streams for a synthetic full job from the same subclient will be 8, even if the Allow Maximum option is selected. If there is no data reader number set, then maximum number of streams for synthetic full job will automatically be set to 1.

  6. Click OK.

Last modified: 1/5/2021 7:58:40 PM