Recover xenserver sr from nas

We want to have a simple setup: xenserver with all vms in a single sr - sr is nfs-mounted from freenas. We have stable and proven backup/recovery of the freenas server. But how can i desaster recover the xensever from the sr on a restored nfs-share? I could not find any description how to reconnect to sr with all the vms. All our vms can boot stable from snapshotted images even if not shut down. I’m sure i’m missing something here.