60700: Acronis Cyber Protect Cloud: "Volume Tracker has failed to open session"

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Last update: 31-05-2021


You are backing up a Hyper-V host.

Warning appears:

Error 0x10c476: Volume Tracker has failed to open session '\Device\HarddiskVolume2' for volume 'C:'.

Error code: 50294
Module: 16
LineInfo: 0xB1CECB03FB1D77AE
Fields: {"$module":"disk_bundle_vsa64_4492"}
Message: Volume Tracker has failed to open session '\Device\HarddiskVolume2' for volume 'C:'.
Error code: 4001
Module: 20
LineInfo: 0xD55ECF00C8D4289E
Fields: {"path":"volume_tracker_driver_api.dll","$module":"disk_bundle_vsa64_4492"}
Error code: 65520
Module: 0
LineInfo: 0xBD28FDBD64EDB8F1
Fields: {"code":"2147942526","$module":"disk_bundle_vsa64_4492"}
Message: The specified module could not be found



Only Agent for Hyper-V is installed, Agent for Windows is not installed.

This warning message indicates that Volume Tracker module is not installed on the machine. Volume Tracker is responsible for tracking changes on the disk and required for CBT (Changed block tracking) technology.

CBT accelerates the backup process: Changes to the disk content are continuously tracked at the block level. When a backup starts, the changes can be immediately saved to the backup. CBT technology option is effective for disk-level backups of virtual machines and of physical machines running Windows.

Warning message "Volume Tracker has failed to open session" usually appears if user is backing up the host with disk-level backup without having Agent for Windows installed.


Agent for Hyper-V backs up virtual machines. To back up the host, you need to install Agent for Windows:

  1. On the affected server, run Acronis Cyber Protect Cloud installation package.
  2. Click Modify the current installation.
  3. In Components to install, click Change.
  4. Select Agent for Windows. Leave all already selected components as is.
  5. Run installation.

Backup should complete successfully now.