1. You back up a Windows machine,
2. Backup finishes with warning "Volume Tracker has failed to freeze checkpoint. A device attached to the system is not functioning"
Volume Tracker is a change block tracking driver that accelerates backup process: changes to the disk or database content are continuously tracked at the block level. This error occurs when Volume Tracker cannot get the necessary data from Microsoft Shadow Copy Provider.
If Volume Tracker was unable to process changes, then you will receive a warning and changes since last backup will be calculated by Agent instead.
There are different possible root causes, see Solution section below.
Beginning with Acronis Cyber Backup 12.5 Update 4 (build 12730) and Acronis Cyber Cloud 8 (build 12960), new performance mechanisms are implemented to the software to improve handling of VSS requests. Please update to the latest available build and check if backup works correctly.
If the issue reproduces on latest build of your Acronis software, check other possible causes:
1) StorageCraft ShadowProtect is installed on the machine
StorageCraft ShadowProtect installs its own VSS provider which is not supported by Volume Tracker module.
To work around the issue, go to Backup Options -> VSS Provider and change the setting to Use Microsoft Software Shadow Copy provider.
2) Operating system is Windows 8
This is a known issue. Please collect Acronis system information from affected agent machine (Acronis Cyber Backup 12.5 - click here for instructions, Acronis Cyber Protect Cloud - click here) and contact Acronis Support with a reference to this article.
3) Check Windows Event log for VSS-related errors and fix the issues.
Open the Windows Event Viewer (press Win+R -> type eventvwr.msc) and check the Windows Logs, Application and System. Look for entries occurring around the time when the issue occurred or just before that.
If suggested steps did not help to resolve the issue, collect Acronis system information from the affected Agent machine and contact Acronis Support: