VADP with hotadd configuration

Helper VM is not required for VADP with ESX 4.0 or above if hotadd mode is selected.  Make sure you do have the necessary license for hotadd.  If VCB is still used in the environment, you can follow Commvault's page "Create a Helper Virtual Machine" on how to configure VCB helper VM.

The following is the properties of the proxy VM before snapshot being mounted. 

After snapshot is created, it will be mounted on the proxy host (which is a Virtual machine).  See screenshot below. 

I have backup 2 VM with one disk on each VM at the same time.  That's why you see two extra virtual disk on the proxy host.  Now, you probably understand why you need Advanced version for ESX 4.1 which include the hotadd feature.  Otherwise, you can only use nbd or san transport mode to backup VM. 

Of course, there is limitation on hotadd such as max vmdk size of 1 TB.

Actually, the 1 TB limitation is no longer valid for VDDK 1.1.1 (http://www.vmware.com/support/developer/vddk/VDDK-1.1.1-Relnotes.html) 

If NBD is used, there is a 1 TB limitation.