Some days ago I’ve got a strange error during the backup job of a vSphere 6.7 (not Update 1) environment with latest version of Veeam Backup & Replication.

The job was starting correctly, VMs have been discoverted, but when the backup start to copy the VMDK the job failed with a “VDDK async operation error 14009” message.

Logs were not much useful to find the problem:

10/21/2018 5:44:34 AM :: Error: VDDK async operation error: 14009. Value: 0x00000000000036b9
Failed to upload disk.
Agent failed to process method {DataTransfer.SyncDisk}.

Also the log files where not helpful in the resolution (the just contained the same error message).

And the Veeam forum it’s filled with other type of VDDK error (for example error 1 and 2) but not this strange error.

I was thinking that was maybe related to the patch for the Veeam Backup & Replication issue with vSphere 6.7 Update 1 (applied to backup a vSAN 6.7U1 cluster), but neither this was the reason.

What I found is that probably was a network issues, but putting a proxy running on the VMware cluster, this issue disapper and the backup (both in network and hot-add mode) was now working well.