VSS Snapshot Creation Delay on Server with DFSR Enabled

Article Applicability

The issue described in this article affects earlier versions of Veeam Agent for Microsoft Windows (VAW), however, the solution provided will only work with VAW 6.1.2 and higher.

Challenge

When backing up a server with the DFS feature enabled, the VSS snapshot creation step in the Veeam Agent for Microsoft Windows (VAW) backup job can take several hours or even days to complete.

Cause

During the VSS preparation phase, Veeam Agent for Microsoft Windows (VAW) prepares VSS writers for a snapshot. When interacting with the DFS VSS writer, VAW can get into a recursion while checking the files within the scope of the DFS writer; this recursion can significantly affect performance. The more files located on the volume with DFS, the longer it takes to finish the preparation steps. The issue is most notably observed on volumes with more than a million files.

Solution

To exclude the DFS writer from the preparation phase, add the following registry key** to the server where Veeam Agent for Microsoft Windows is installed**:

**Note:**This registry value requires at minimum Veeam Agent for Microsoft Windows 6.1.2.134.

Key Location: HKLM\SOFTWARE\Veeam\Veeam Endpoint Backup\ **Value Name:**VSSExcludeDFSWriter **Value Type:**DWORD (32-Bit) Value Value Data: 1

Set registry value using PowerShell:

New-ItemProperty -Path 'HKLM:\SOFTWARE\Veeam\Veeam Endpoint Backup\' -Name 'VSSExcludeDFSWriter' -Value "1" -PropertyType DWORD -Force

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