Transport Modes for VMware

By default, the transport mode is selected automatically for backups and restores, based on the VSA proxy used and the virtual machines being backed up or restored. You can force a specific transport mode by configuring it at the subclient level, or by configuring the vStorageTransportMode additional setting for all proxies that are used by a vCenter client.

The following transport modes are available in VMware. Advanced transport methods (SAN and HotAdd) replace the proxy-based VMware Consolidated Backup (VCB) solution.

  • SAN (storage area network) - SAN mode is supported for directly connected storage using Fibre Channel (FC) or Internet SCSI (iSCSI) protocols.
  • HotAdd - In HotAdd mode, the Virtual Server Agent is installed on a virtual machine residing on an ESX Server.

    Licensing: In vSphere 5.0, the SCSI HotAdd feature is enabled only for vSphere editions Enterprise and higher, which have Hot Add licensing enabled.

  • Local Area Network (NBD and NBDSSL) - NBD (network block device) & NBDSSL (encrypted NBD) transmit data over the TCP/IP connection between the ESX server and the proxy computer.
  • NAS (network attached storage) - The 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).

SAN and HotAdd transport can enable LAN-free backups and restores. In most scenarios, backups and restores using SAN and HotAdd transport are faster than local area network (LAN) operations using network block device (NBD) or secure NBD (NBDSSL).

SAN restores using thin disk provisioning can be slower than LAN restores; performance can be improved by using NBD or by setting the transport mode to SAN and forcing the disk type to thick, which uses eager zero provisioning.

The following table summarizes the configurations based on the storage type:


Datastore Storage Type

VM Data Protected by Single Node

Additional Comments

LAN Free SAN mode

VMFS using Fibre Channel or iSCSI

Up to 40 TB

Virtual Server Agent and MediaAgent installed on the same physical computer with direct connection to datastore.

Eliminates data transfer over network during backup and restore. Provides best backup and restore performance.

LAN Free HotAdd mode


Up to 30 TB

Virtual Server Agent and MediaAgent installed on virtual machine running on host with access to datastore.

Eliminates data transfer over network during backup and restore.

Network based (NBD, HotAdd, NAS)

VMFS, NFS, vSAN, VVol, direct attached storage

Virtual Server Agent and MediaAgent installed on different computers. The Virtual Server Agent writes over the network to a remote MediaAgent.

Depends on infrastructure.


Configure DNS on the backup gateway, ESX hosts, and vCenter Server. For any transport mode, a missing or incorrect DNS configuration produces nslookup errors during fully qualified domain name (FQDN) resolution.

Related Topics

Last modified: 12/18/2019 9:40:03 PM