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Full Restore Point Generated by Veeam Agent for Microsoft Windows Cluster Backup Is Larger Than Source Cluster

KB ID: 4476
Product: Veeam Backup & Replication
Veeam Agent for Microsoft Windows
Published: 2023-08-18
Last Modified: 2023-08-18
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Challenge

The Backup Job for a Failover Cluster, or its associated Backup Copy Job, generates full (.vbk) restore points that are larger than the source Failover Cluster.

Cause

During the cluster backup, Veeam Agent for Microsoft Windows will deduplicate the blocks within shared disks. However, if the cluster disk(s) size is greater than 64 TiB, some blocks may not be deduplicated, causing the restore point to be substantially larger than the source.

Solution

Potential Performance Impact
In rare circumstances configuring the DedupeIndexLimit to such a high value may reduce backup performance. You may contact Veeam support before proceeding with these steps, and we can assist with evaluating whether this is likely to happen, or you may proceed and create a support case should any performance issue occur.
  1. Create the following registry value on the machine where the target VeeamAgent process operates.

    Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication
    Value Name: DedupeIndexLimit
    Value Type: DWORD (32-bit) Value
    Value Data(Dec): 16777216 

    Default value is 8388608
    • For Windows repositories,  the target VeeamAgent process operates on the Windows machine itself.
    • For NFS and SMB repositories, you should assign a dedicated Gateway server and create the registry value on that machine.
    • For Linux repositories, this setting is controlled by creating the file /etc/VeeamAgentConfig and adding the following entry to it:
      DedupeIndexLimit=16777216
      
  2. Within Backup Job for the Failover Cluster, ensure that the Storage Optimization (block size) has been set to 4MB.
  3. Force the Backup Job for the Failover Cluster to perform an Active Full.

More Information

If you have any questions or concerns, please create a support case for assistance.
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