Mounting a volume for VCB backup fails with "Failed to open the disk:..." in the log (4042481)

Date: May 08
Product & Version: All NVBU
OS Version: Windows
Module & Version: All VMware plugins
Application version: All ESX server versions

Symptoms:
When right-clicking and trying to mount a volume from a Windows machine on your VCB proxy this fails and you can not browse the folders.

Reason:
For this operation, VMware invokes the vcbMounter utility of the VCB framework. It is this VMware utility that fails.

There are several potential reasons for this:
a) This usually means that the VCB proxy cannot access the shared storage the virtual machine is located on. Try using the network transport mode in vmware.cfg (documented in chapter 8.3 of the manual). If the machine can be mounted over the network, the problem is with the storage configuration on the VCB Proxy.

b) Not all combinations of VCB framework, storage and ESX Server are supported by VMware. For example, even though you can create a virtual machine on an iSCSI LUN with ESX Server 3.0.1, backup of such LUNs through VCB is only supported with ESX Srver 3.0.2 and higher.

c) The LUN needs to be available to both the ESX Server and the VCB Proxy. Also, the LUN numbers need to match on both - if you use LUN masking/zoning, this might not be the case, leading to the VCB Proxy looking for a LUN where it can't find one. You can check this in Disk Management on your VCB Proxy.