Disk Image backup error in Comet Backup: "Disk '[GUID]' selected, but does not exist on the local system"

Symptoms

• During a Disk Image backup job, the backup fails with the following error message in the job log:

  PRODUCT_WARN: Disk '[GUID]' selected, but does not exist on the local system

• The backup job completes with an Error status if no disk is backed up, or Warning status if at least one was backed up.

Cause

Comet generates Disk IDs (a hash of disk values, partition layout, and other parameters) instead of using disk or volume GUIDs, to protect against duplicated virtual disks. 

The disks on the endpoint no longer match this identifier (e.g., due to a disk layout change, partition alteration, or system update).

Resolution

Reselect the disks in the Protected Item picker, so that the Protected Item is updated with the new disk and partition IDs.

1. Open the Comet Backup client interface on the target device (or access it via the Comet Server Web Console).

2. Navigate to the affected Protected Item settings (Disk Image type).

3. Reselect the partitions or disks to be included in the backup.

4. Save the configuration changes.

Note: If this happens frequently on a Windows endpoint, reconfigure the Protected Item to target partitions by Drive Letter rather than Disk ID. Change the selection mode/configuration to select disks by Drive Letter instead of Disk ID.