iscsi_helper=ietadm raises error when creating the volume

Has anyone tried set iscsi_helper=ietadm under devstack. I changed iscsi_helper in /etc/cinder/cinder.conf, then I got the error when creating a volume.

=================================Log of c-vol========================================
2012-10-22 18:20:57 DEBUG cinder.volume.manager [req-bae80ab0-36d5-4726-9b7e-c997b4cbd737 91bb02e4220c457d8406e664c971e2bd 1ce7f667cc2047f18ffc8e0c6e0ccba8] volume volume-6c4c25c6-c1d9-4e66-9720-244d8943b2c7: creating export from (pid=23320) create_volume /opt/stack/cinder/cinder/volume/manager.py:155
2012-10-22 18:21:00 DEBUG cinder.utils [req-bae80ab0-36d5-4726-9b7e-c997b4cbd737 91bb02e4220c457d8406e664c971e2bd 1ce7f667cc2047f18ffc8e0c6e0ccba8] Running cmd (subprocess): sudo /usr/local/bin/cinder-rootwrap /etc/cinder/rootwrap.conf ietadm --op new --tid=1 --params Name=iqn.2010-10.org.openstack:volume-6c4c25c6-c1d9-4e66-9720-244d8943b2c7 from (pid=23320) execute /opt/stack/cinder/cinder/utils.py:163
2012-10-22 18:21:00 DEBUG cinder.manager [-] Running periodic task VolumeManager._publish_service_capabilities from (pid=23320) periodic_tasks /opt/stack/cinder/cinder/manager.py:164
2012-10-22 18:21:00 DEBUG cinder.manager [-] Running periodic task VolumeManager._report_driver_status from (pid=23320) periodic_tasks /opt/stack/cinder/cinder/manager.py:164
2012-10-22 18:21:00 DEBUG cinder.utils [req-bae80ab0-36d5-4726-9b7e-c997b4cbd737 91bb02e4220c457d8406e664c971e2bd 1ce7f667cc2047f18ffc8e0c6e0ccba8] Result was 145 from (pid=23320) execute /opt/stack/cinder/cinder/utils.py:180
2012-10-22 18:21:00 ERROR cinder.openstack.common.rpc.amqp [-] Exception during message handling
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp Traceback (most recent call last):
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/openstack/common/rpc/amqp.py", line 276, in _process_data
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp rval = self.proxy.dispatch(ctxt, version, method, **args)
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/openstack/common/rpc/dispatcher.py", line 145, in dispatch
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp return getattr(proxyobj, method)(ctxt, **kwargs)
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/volume/manager.py", line 163, in create_volume
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp volume_ref['id'], {'status': 'error'})
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp self.gen.next()
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/volume/manager.py", line 156, in create_volume
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp model_update = self.driver.create_export(context, volume_ref)
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/volume/driver.py", line 382, in create_export
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/volume/iscsi.py", line 200, in create_iscsi_target
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp self._new_target(name, tid, **kwargs)
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/volume/iscsi.py", line 213, in _new_target
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp **kwargs)
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/volume/iscsi.py", line 60, in _run
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp self._execute(self._cmd, *args, run_as_root=True, **kwargs)
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp File "/opt/stack/cinder/cinder/utils.py", line 187, in execute
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp cmd=' '.join(cmd))
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp ProcessExecutionError: Unexpected error while running command.
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp Command: sudo /usr/local/bin/cinder-rootwrap /etc/cinder/rootwrap.conf ietadm --op new --tid=1 --params Name=iqn.2010-10.org.openstack:volume-6c4c25c6-c1d9-4e66-9720-244d8943b2c7
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp Exit code: 145
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp Stdout: ''
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp Stderr: 'Connection refused.\n'
2012-10-22 18:21:00 TRACE cinder.openstack.common.rpc.amqp