With Backup&Replication 8 Update 2 Veeam added support for backing up vVol-based VMs. There is nothing special to do to backup those VMs but simply create backup jobs and include them as you would do with any VMFS datastore based VM. The only important thing to remember is that vVol based VMs can currently only be backed up in NBD or hot-add mode. The reason for this limitation is because vVols are a VMware-related special construct that needs a special presentation schema from the storage system as well as special drivers for the HBA to support it. You can see the requirements for using vVols with a 3PAR system in this article.
One of the mentioned requirements is to set the host property within the 3PAR system to use the 11-VMware persona. With this persona there will be a meta device presented, the so called Protocol Endpoint meta device. This is the entry point for the vSphere host to create vVol 1:1 mappings between VM objects and storage LUNs. This PE device will only be presented to hosts with the VMware persona. As your physical Veeam backup server is a Windows system, you have to choose the Windows persona for that server and thus the PE meta device can't be presented to the host. Furthermore the special FC drivers you need to detect the PE device are not available for Windows.
So to cut a long story short: currently backups of vVols in SAN mode is NOT SUPPORTED.
This is a bit of a drawback as SAN mode is the most used backup transport mode and if you choose to use vVols you want to benefit from the improved possibilities and performance and don't want to switch back to hot-add or even NBD mode. But at the moment you have to.
This will probably result in a reconfiguration of your backup infrastructure. In my test lab I have only a single physical backup proxy that has configured SAN mode as preferred transport method and failover to network is not allowed. This will cause my vVol backup job to fail. After allowing fallback to NBD the job runs flawless (ignore the guest agent warning, this is only due to wrong credentials):
In the 3PAR VSP you won't see any activity in the "Recent task" pane, but if you choose "Manage system alerts, view system events" and then go to the Events tab and get the events for the last hour, you will see what's going on:
BTW, backup of vVols do not need the Enterprise Plus Edition of VBR that brings storage integration. Although the CLI commands on the 3PAR system are done from the Veeam server, there is no need to add the 3PAR system into Veeam under "Storage Infarstructure". The Veeam server collects all needed information about the 3PAR from the vCenter server at backupjob runtime. Backup of vVols can therefore be done even with the Standard Edition.
So backup of vVol backed VMs is quite easy as long as you remind the transfer method requirements. I always prefer to avoid using NBD as long as I'm in a 1GbE network (remember, NBD uses the service console kernel adapter that is limited to ~30% of maximal bandwidth, so in a 1GbE network you will only have 300MBit for backup data....). Things change if you have 10GbE, than NBD is nearly as fast as hotadd or even SAN mode.
My recommendation is to setup one or more virtual Veeam proxy VMs that are being used exclusively for backup vVol VMs and let the physical proxy (as long as you have one) do the rest within the SAN.