Several transport modes are supported depending on how your infrastructure is configured. For VMware vSphere setups, the following apply. The Veeam transport service runs on the backup proxy server, which can also be the backup server itself, and is configured there. For retrieving data, the following three modes are offered through the vSphere APIs for Data Protection (VADP):
Direct SAN Access: This is the most efficient method of transfer and is available if you have installed the backup proxy server on a physical server with direct Fiber Channel access to the SAN. For iSCSI SAN setups, the proxy server can be installed either on a physical host or on a virtual host that has direct access to the SAN.
Virtual Appliance: This mode is available if the backup proxy is installed on a virtual machine and works by utilizing SCSI hot-add to attach the disks of the backed-up VM to the backup proxy VM, thus not traversing the network when performing the backup.