I'm using VDR on vsphere 5.0. Since I need to backup to network, I can't upgrade to VDP, yet. However, I would like to upgrade my hosts to vSphere 5.1 so that I can use other new features such as replications. Can VDR run on vSphere 5.1?
Yes but it that configuration is not supported by VMware. I have ran VDR in a test environment where it started out as vCenter 5.0 and ESXi 5.0 with VDR and I upgraded both vCenter and ESXi to versions 5.1 and the VDR appliance still function both backup and restores, but like I said this configuration is not supported.