Veracrypt Breaks Windows Backup and Restore

[gashtal]

As long as there is any Veracrypt drive currently mounted, the "Create a system image" functionality of Windows Backup and Restore fails to detect any target drives to store the image in with error "Incorrect function". The only work-around is to either dismount all Veracrypt drives, or to mount them as a "removable medium". This is 100% reproducible on any version of Windows 10 and 11. The issue is possibly related to: #476

Steps to reproduce

1. Mount a Veracrypt partition or container
2. Go to Control Panel\System and Security\Backup and Restore (Windows 7)
3. Open "Create a system image"
4. You will see "Incorrect function" error (screenshot below) when Windows is searching for target drives
5. Dismount the Veracrypt partition, or remount as "removable medium" and repeat
6. The error no longer happens

Screenshots

Your Environment

Please tell us more about your environment

VeraCrypt version: 1.26.24

Operating system and version: Windows 11 25H2 -- issue happens on every version of Windows 10 and 11

System type: 64-bit

[idrassi]

Thank you for the report.

This issue is most likely caused by Windows Backup enumerating mounted fixed disks and expecting them to support volume/disk extent queries used by system-image/VSS workflows.

There are two different cases:

1. File-hosted containers: These should be mounted as removable media when using Windows Backup. VeraCrypt cannot safely expose real physical disk extents for file containers, especially because the container file may be fragmented or moved by the host filesystem.

2. Device-hosted/partition-hosted VeraCrypt volumes: These can remain mounted as fixed disks, but you should enable "Allow Windows Disk Defragmenter to defragment non-system partition/drive" in Settings > Performance/Driver Configuration. This enables the driver to answer IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS for raw/device-hosted VeraCrypt volumes. Windows Backup likely needs this information while enumerating possible system-image backup targets.

So the recommended workaround is:

• Mount file containers as removable media.
• Mount device-hosted/partition-hosted volumes as fixed disks.
• Enable Allow Windows Disk Defragmenter to defragment non-system partition/drive.

This is not the same as full VSS support for VeraCrypt virtual volumes but it should avoid the Windows Backup enumeration failure in the common device-hosted case.

Please test with this configuration and report whether Windows Backup still shows the “Incorrect function” error.

If confirmed, we will update the documentation to make this workaround explicit.