Symptoms
Incremental backup of one VM causes the Workflow to hang after backing up some data.The issue is persistent for this same VM, and the workflow appears to hang after backing up the same amount of data each time. The VM backup session log indicates backup request progresses as normal. The snapshot is created, and the data mover starts to move the data, and then backup halts, with no error, no indications on the issue, there is no log entry for several hours, or until the backup admin cancels the backup task. By canceling the backups proxyHC cleanup is required and at times vmconfig unlock is also required, to retry the VM backups, but the stall at the same point as previously observed.
NVP-vProxy: How to use health check tool ProxyHC on vProxy applianceNetWorker: NVP - VProxy - Failed to lock Virtual Machine for backup: Another vProxy operation is active on the VM
All other VM backups work with no issues.
Cause
There is an issue with VMware Change Block Tracking (CBT) for the VM observing this symptom. CBT is used during incremental VM backups for calculating what changed data must be backed up.
Resolution
Reset CBT based on the following VMware KBSchedule downtime for steps 1-11 from this KB: https://kb.vmware.com/s/article/2139574 Step 12 is automatically done by vProxy during backup.
