Longhorn on RancherOS RBS

RancherOS 1.4.0
Rancher 2.0.6

Is Longhorn possible on RancherOS ?
i’ve run sudo ros s enable open-iscsi and tried the Helm package from Rancher Server v2 but am getting:

ERRO[0000] Failed environment check, please make sure you have iscsiadm/open-iscsi installed on the host
FATA[0000] Error starting manager: Environment check failed: Invalid mount namespace /host/proc/1/ns/mnt, error Failed to execute: nsenter [–mount=/host/proc/1/ns/mnt mount], output nsenter: failed to execute mount: No such file or directory
, error exit status 1

Is Ceph or ZFS a better way to go ?