Networker Support for Xen Server?

I am struggling to find a good way to backup Xen Server at the hypervisor level, similar to what VMware enables via the Vstorage API.

In this particular customer account, we have Xen running on NFS shares within a VNXe, so, I'm thinking that NDMP backups of the NFS file systems can be done, but not sure about quiescing the VM's through a Xen-provided API for with VSS integration, etc.

Any thoughts on this?