Unexpected Volume Shadow Copy Service (VSS) Error Has Occurred (code 2407)

Situation

A backup plan terminates with the following error: Unexpected Volume Shadow Copy Service (VSS) error has occurred

The event log contains the following ID: 8193

The research of the log files gives more details about the failure and explains the reason behind it:

VSS Error 12/7/2018 8:23:12 AM EventID: 8193 Volume Shadow Copy Service error: Unexpected error calling routine Cannot find anymore diff area candidates for volume \?\Volume{ae7c3d9e-5755-11e1-9069-806e6f6e6963}\ [0]. hr = 0x8000ffff, Catastrophic failure.

Operation: Automatically choosing a diff-area volume Processing EndPrepareSnapshots

Context: Volume Name: \?\Volume{ae7c3d9e-5755-11e1-9069-806e6f6e6963}
Volume Name: \?\Volume{ae7c3d9f-5755-11e1-9069-806e6f6e6963}
Execution Context: System Provider

Cause

This error means that the system does not have enough disk space to create a shadow copy during a backup. You need to increase the area allowed to VSS to buffer such write operations.

Solution

To work around the issue, increase the shadow copy storage area for the volume reported in the error message: \?\Volume{ae7c3d9e-5755-11e1-9069-806e6f6e6963}

To find the value of the affected volume, do the following:

  1. Run Command Prompt as Administrator and type the command mountvol which will give you a list of all possible values for the current mount points.

  1. Find the value associated with the volume, then proceed to increase the size of the shadow copy storage area for this volume

  2. Run Command Prompt as Administrator to list all existing shadow storage associations with the following command:

vssadmin list shadowstorage 

  1. If the output for the command is "No items found that satisfy the query" - then no association exists for the reported volume. To proceed, add shadow storage for that volume manually using the following command
vssadmin add shadowstorage /for=<ForVolumeSpec> /on=<OnVolumeSpec> [/maxsize=<MaxSizeSpec>] 

For example, the command which adds the shadow storage area of 200 GB in size for a 1 TB volume with a label D will be the following

vssadmin add shadowstorage /for=D: /on=D: /maxsize=200GB
  1. If a shadow storage association already exists you will need to resize the shadow storage area:
vssadmin resize shadowstorage /for=<ForVolumeSpec> /on=<OnVolumeSpec> [/maxsize=<MaxSizeSpec>]

Resizing the storage association may cause shadow copies to disappear.

When no shadow storage association exists for a volume, the shadow copies utility will display 10% of the volume or MinDiffAreaFileSize, whichever is greater. However, Windows may set a different maximum size during shadow copy creation. While the default behavior works well for most volumes, setting a limit of 15-20% of the total volume size may be needed on busy servers.

References:

  1. Vssadmin list shadowstorage
  2. Vssadmin add shadowstorage
  3. Vssadmin resize shadowstorage

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