This issue has been observed to occur under two different scenarios:
When an SMB Share repository is added to Veeam Backup & Replication, if that SMB Share advertises that it is capable of certain features, Veeam Backup & Replication will mark the repository as being Fast Clone compatible. While SMB shares are supported for Fast Clone, there are certain specific requirements. In rare cases, Veeam Backup & Replication may assume, based on the reported capabilities of an SMB share, that the SMB share is compatible with Fast Clone when in fact, the underlying storage of the NAS is not actually Fast Clone compatible.
This issue has been observed as occurring most often with Synology devices, though other NAS devices may be affected.
Registry Setting to Disable Fast Clone for SMB
The following registry value force Veeam Backup & Replication to never use Fast Clone with SMB shares.
It must be created on the Veeam Backup Server.
Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
Value Name: UseCifsVirtualSynthetic
Value Type: DWORD (32-Bit) Value
0 = Disable using Fast Clone with SMB Share
1 = Enable using Fast Clone with SMB Shares
- This value takes effect on the next job run. There is no need to restart the Veeam services.
- This setting will disable Fast Clone functionality for all SMB repositories.
PowerShell Cmdlet to create Registry Value to Disable Fast Clone for SMB