This issue occurs because the consolidation attempt is made prior to the backup proxy lease being cleaned up.
The series of events should match:
- Backup starts
- Snapshot created for backup
- Lease established
- Failure of SAN mode, then fallback to NBD mode
- Backup finishes
- Consolidation attempt (fails)
- Lease released
Note: The backup proxy must be a separate physical machine to trigger the issue; virtual machine based proxies cannot access SAN mode backups.
This is a known issue affecting the Virtual Disk Development Kit (VDDK) 5.0 / 5.1.
After the lease is released, normal consolidation is possible.
To work around this issue, configure the backup software to attempt NBD directly instead of attempting SAN-based backup first, or ensure the correct block devices are present on the backup proxy server prior to attempting a SAN-based backup.
Note: Auto mode attempts SAN-based backup first then falls back to NBD if that fails. This situation will also trigger the issue
VMware is planning to address the orphaned lease in a future release of the VDDK.