Proxmox VE backup in Comet Backup ends with a warning: "no block device "drive-scsi0" found in query-block"

Symptoms

A Proxmox VE backup job in Comet Backup completes with the warning:

PRODUCT_WARN: Failed to close disk scsi0 for VM 100: Resolving node to close bitmap for disk drive-scsi0: no block device "drive-scsi0" found in query-block

Cause

This is a Comet Backup bug with ID COMET-61019.

During cleanup, the Comet Backup agent looks up the disk by its name (for example, `drive-scsi0`) in the QEMU `query-block` output to prune old change block tracking (CBT) bitmaps. Proxmox VE 9 starts QEMU with `-blockdev`, so the lookup returns nothing and the job ends with a warning. The backup data is intact, and the only side effect is that old CBT bitmaps are not pruned. 

Resolution

A fix for the bitmaps being left open is in progress. Monitor Comet Backup release notes for the fix labelled with the issue ID COMET-61019.