Configuring Transport Modes for VMware

By default, the software automatically determines the transport mode currently being used in your environment prior to each backup operation. This process can be eliminated by configuring the subclient to use a specific transport mode for all backups of that subclient. Doing so negates the need for the software to search your environment for the appropriate mode, thereby increasing backup performance.


  1. From the CommCell Browser, expand Client Computers > virtualization_client > Virtual Server > VMware > backup_set.
  2. Right-click the subclient and click Properties.
  3. Click the Transport Mode for VMware list and select any of the following transport modes:
    • Auto (default) - The transport mode is selected automatically based on the backup environment:
      • If the datastore for VMDKs is accessible to a physical proxy, SAN mode is used.
      • If the datastore for VMDKs is accessible to the ESX server for a virtual proxy, HotAdd mode is used.
      • Otherwise, NBD mode is used.
    • SAN - For directly connected storage using Fibre Channel (FC) or Internet SCCI (iSCSI) protocols. The Virtual Server Agent must have zoning or mapping to the storage array with access to snapshots of the datastore LUNs (logical drives) that provide storage for virtual machine disks. Data is read directly from the storage where virtual machines reside, without going through the ESX host or transferring data over the local area network (LAN). The ESX host is contacted only to coordinate access to the LUN. SAN transport mode cannot be used if the proxy computer is a virtual machine.
    • HotAdd - The Virtual Server Agent is installed on a virtual machine residing on an ESX Server. In HotAdd mode, the data volumes containing the virtual machines to be backed up are automatically mounted to the proxy, so they can be accessed by the proxy as a local disk. The ESX host the proxy is running on must have access to all datastores for the virtual machine. If the virtual machine and the proxy are not on the same host, all datastores must be shared between the hosts.

      Licensing: In vSphere 5.0, the SCSI HotAdd feature is enabled only for vSphere editions Enterprise and higher, which have Hot Add licensing enabled. No separate Hot Add license is available for purchase as an add-on. In vSphere 4.1, Hot Add was also enabled in the Advanced edition. Customers with vSphere Essentials or Standard editions are not able to perform proxy-based backup, which relies on SCSI HotAdd. Those customers must use alternate transport modes.

      SCSI Controllers: HotAdd relies on the SCSI protocol. With VDDK 6.5 or later, VMware recommends the paravirtual SCSI (PVSCSI) controller. (For more information, see Virtual Disk Development Kit Release Notes.) For older VDDK versions, use the LSI SCSI controller. HotAdd does not support IDE disks.

    • NBD - Data is transferred using the TCP/IP connection between the ESX server and the proxy computer. The local area network (LAN) can be the production network or a dedicated backup network.
    • NBDSSL - Similar to NBD mode, but data transfer between the proxy computer and the ESX server is encrypted. Encryption should be used for sensitive information, even within a private network.
    • NAS - NAS (network attached storage) transport mode enables the virtual server agent (VSA) proxy computer to read data directly from the network file server (NFS), without going through an ESX host or transferring data over the local area network (LAN).
  4. Click OK.

Last modified: 3/12/2019 4:02:00 PM