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Configuring Dynamic Stream Allocation

When data is not distributed equally across all of streams on the source copy, then one stream might take longer to copy than another. You can avoid this situation by distributing data across multiple streams.

Auxiliary Copy operation is performed with a fixed mapping between the source and destination streams. If the original backup data was not distributed evenly in the source streams, the Auxiliary Copy operation may not use all of the available streams simultaneously. In such a situation, enabling Stream Randomization helps to distribute data evenly among streams. However, if a sufficient number of drives are not available for each stream during an Auxiliary Copy operation, the stream randomization might be ineffective. Dynamic Stream Allocation feature allows you to distribute data evenly across available streams and is most effective when the source copy is on a disk. This feature cannot be used when source copy is on tape because it cannot read randomly from tape media.

Dynamic Stream Allocation feature can also be used for the following operations to distribute the data between streams:

  • Content Indexing
  • Data Verification
  • Deduplication Database (DDB) Reconstruction

    When this feature is enabled, for these operations, the stream settings that are specified on the Copy Properties - Media tab have no effect, and dynamic stream allocation uses maximum number of device streams that are set in the Storage Policy properties.

You can enable this feature in the following scenarios:

  • When the Combine Source Data Streams and Multiplex source streams options are enabled for the a secondary copy.
  • When multiple Storage Policies are using same library and Auxiliary Copy jobs for all the storage policies are scheduled at the same time.
  • When some drives from the tape library are offline for long time.

Note: When this option is enabled during Auxiliary Copy operation, the values of Total data to Process in the General tab of Auxiliary Copy Job Details dialog box and the sum of Total Data to View Jobs in the Jobs for Storage Policy Copy window will differ.

Procedure

  1. From the CommCell Browser, expand Policies > Storage Policies.
  2. Right-click the appropriate storage policy, and then click Properties.
  3. Select the Distribute data evenly among multiple streams for offline read operations check box, to distribute backup data evenly across multiple streams.
  4. Click OK.