Sorry. . . It shouldn't be this hard to explain. But in the case of my client. They have a Barracuda Backup 690. It has the ability to take vmware machine snapshots and store them on the barracuda device. It also can replicate those off-site. FreeNAS currently requires the datastore to be hosted on the FreeNAS box to do Vmware snapshots. The barracuda doesn't. So I assume there's some API that reaches out to vsphere, takes the snapshot, and exports it to the Barracuda Backup 690.
Please let me know if you need more info, maybe I can find a better article/example.
Barracuda Description of the Vmware Feature on it's Backup appliance.
"Virtual Machine Integration
Organizations running Microsoft Hyper-V or VMware vSphere have flexible backup options that include guest and image-level backups. In both platforms, only new, changed, deduplicated data chunks are transferred across the virtual/physical infrastructure. Barracuda leverages VMware’s Changed Block Tracking (CBT) for faster backups and restores. Barracuda provides fast, easy recovery of individual files or complete VM images to the original VMware, an existing VMware or a new VMware."
