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Scale-out Backup repositories

Data locality or performance mode?

Since the introduction of Fast Cloning on ReFS and XFS the Data locality mode is the recommended setting for most deployments due to the space savings and efficiency of synthetic operations. The performance mode is only recommended for very specific use cases.

SOBR Reserve Space

With a SOBR VBR will reserve 1% of the available extent space to allow for the update of metadata files. These values can be modified by changing registry keys; however, it is not recommended.

In cases where 1% of the total capacity is significant storage, the reserve can be reduced by modifying the SobrReserveExtentSpacePercent registry setting.


  • Key: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
  • Type: REG_DWORD
  • Default value: 1 (percent)

However, this setting should be modified with caution, as insufficient space can cause issues with backup transformations.

SOBR Free Space Calculation

Free space data is only retrieved when no active tasks are assigned to an extent. In environments where tasks are always running the estimated capacity may differ from the free space. This may result in an error that there isn’t sufficient space.

To resolve this, you can update another registry key making the checks time-based.


  • Key: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
  • Type: DWORD
  • Default Value: 0

0 - (Default) Only retrieve actual free space when there are no active tasks assigned to an extent.

1 - Enable periodic recalculations of estimated free space.

Block size

The created data-block-objects in the object storage are based on the backup’s configured block size (Storage optimizations)

The default is 1MB which refers to the uncompressed block size.

Every block is offloaded as a single object in the object storage and thus requires one API call per read or write operation (GET/PUT).

For the same amount of data, a larger block size would mean less objects and less API calls. On the other hand, larger block sizes creates significantly larger incremental backups. It also means a higher probability of changes in the block which reduces the efficiency block cloning.

Experience shows that the default Optimal compression setting with the 1MB block size is the best choice for most environments.

However, specific Object Storage providers may have different recommendations, in many cases 4MB is recommended to reduce the number of API calls.

Please check with the Object Storage vendor for their recommendations.


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