[Users] Switching storage type?

Hi, Is it possible to switch a storage type with VMs still on it? I have a datacenter with a local storage and I want to switch it to NFS (or Gluster). Setting up the NFS on the directory is not a problem but I can't detach the storage with VMs on it. The next question would be if I could import the domain as NFS if it was a local storage before. TIA mad