SCS KB 1006: VSS Utilization percent being reset by backup plan

Use Case:

When a backup is in progress, the pre-defined VSS usage percentage is overwritten by the software in order to complete the backup at a proper pace. For example, if VSS usage is limited to 10%, it will be set to 100% during the backup and back down to 10% after the backup is complete.

Symptoms:

VSS Usage percentage is not set back to pre-defined value after backup.

Root Cause:

This issue is commonly caused by a backup being interrupted. Running a successful backup may not revert the value back to the default set previously, as the value when this backup starts is still at 100%.

Solution:

1. Manually re-adjust the VSS usage percent if a backup is interrupted and the value remains at 100%.

2. Development team is tracking this issue and a fix will be introduced in future versions.

Workaround:

If backups are prone to being interrupted and this issue happens frequently, you can set the following parameters on your backup plans to reset the VSS usage before the backup starts.

1. Edit the backup plan
2. Advanced options
3. Pre-post commands

4. Execute a command before the backup: YES
    
   Command or batch file path on the machine with an agent: vssadmin
    
   Arguments: resize shadowstorage /on=C: /for=C: /maxsize=[VALUE%] 

For example: