Does Unitrends support VVOLs?


Does Unitrends support VVOLs?  If so, what transport modes are available?


Supported Transport Modes

A VMware Backup Host can access Virtual Machine data from datastores using four different methods – SAN, LAN(NBD), HotAdd and NBDSSL. These methods are referred to as VMware Transport modes.

  • SCSI HotAdd: Supported with VVol (This would be available with UB only)

When running VMware Backup Host on a Virtual Machine, vStorage APIs can take advantage of the SCSI Hot-add capability of the ESX/ESXi server to attach the VMDKs of a Virtual Machine being backed up to the VMware Backup Host. This is referred to as HotAdd transport mode. With VVols, the backup proxy is a VM, and the snapshots that are to be backed up are attached in something of a “read-only” mode* to the backup proxy as a virtual scsi disk. 

* It is not exactly read-only mode, it is attached as a independent nonpersistent disk, which means that any writes to this “read-only” VVol object are redirected to a temporary object that get destroyed when the VM is powered off or the disk is removed.

  • Network Block Device (NBD): Supported with VVol

In this mode, the ESX/ESXi host reads data from storage and sends it across a network to the VMware Backup Host. As its name implies, this transport mode is not LAN‐free, unlike SAN transport. This method is not as efficient as it uses the network stack instead of the storage stack.

  • NBDSSL: Supported with VVol

NBDSSL is the same as NBD, except that NBDSSL uses SSL to encrypt all data passed over the TCP/IP connection.

  • SAN Transport Mode: Not Supported with VVol

For today’s VMFS disks, SAN transport mode relies on a proxy VM to tell the backup appliance which blocks it should read (since the Windows OS on the backup system can’t directly mount a VMFS disk). With VVols we use the VASA API to establish a “binding”, something of a “handshake” between the ESX host and the VASA provider, which not only instructs the VASA provider to “construct” a data path for the VVol for the ESX host, but also provides the requisite information needed by the ESX host to construct the data path on the ESX side.  Because physical backup proxies cannot be VASA clients, currently, it is impossible to construct a “direct” data path between the VVol storage and the Physical Backup Proxy.

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