VBR leverages VMware VADP to transport VM data directly from and to FC and iSCSI storage over the SAN. VM data travels over the SAN, bypassing ESX(i) hosts and the LAN.
Data Retrieval in Direct SAN Access Mode is described in the user guide
1.The backup proxy sends a request to the ESX(i) host to locate the necessary VM on the datastore.
2.The ESX(i) host locates the VM.
3.The ESX(i) host retrieves metadata about the layout of VM disks on the storage (physical addresses of data blocks).
4.The ESX(i) host sends metadata to the backup proxy.
5.The backup proxy uses metadata to copy VM data blocks directly from the storage via the SAN.
6.The backup proxy processes copied data blocks and sends them to the target.
Note that backup proxy using the Direct SAN Access transport mode must have a direct access to the production storage via a hardware or software HBA. If a direct SAN connection is not configured or not available when a job or task starts, the job or task will fail.