Symptoms

Scheduled VADP backup fails (on ESX 5.5) with below error intermittently. The backup job also hangs during the process with no data transfer.

Error: GetBackupSessionFiles failed. error: Cannot connect to the host (VixDiskLib_Open returned error code: 18000) ([XXX-ESX02-Local] XX-XX/ABC.vmdk) Failed OpenListing for vcenter6.XX.com\FolderName\

Cause

1. The client network was not configured correctly to allow direct access to the ESXi hosts from the ds-client server network.

2. Might be due to the number of VMs backed up concurrently.

https://www.vmware.com/support/developer/vddk/vddk-602-releasenotes.html.

Workaround

1. Re-provision the IPv4 interfaces on the DS-Client host and started to observe wire speed transfer rates, no more errors.

2. Reschedule the backup to ensure not too many VMs are run concurrently.