I was also not able to attach to vdc which was not already there. There were no errors while devstack was doing the nova volume stuff.

Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,190 AUDIT nova.api.openstack.v2.contrib.volumes [229ab0dc-3085-4f4c-bb80-d8104c96b\
ef8 demo 2] Attach volume 1 to instance 3d37d21e-8fba-46a4-a0e1-d137f1d17597 at /dev/vdc
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,265 DEBUG nova.rpc [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] Making asynchrono\
us cast on compute.xg06... from (pid=8466) cast /opt/stack/nova/nova/rpc/impl_kombu.py:784
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,268 DEBUG nova.rpc [-] received {u'_context_roles': [u'Member', u'sysadmin', u'net\
admin'], u'_context_request_id': u'229ab0dc-3085-4f4c-bb80-d8104c96bef8', u'_context_read_deleted': u'no', u'args': {u'instance_\
uuid': u'3d37d21e-8fba-46a4-a0e1-d137f1d17597', u'mountpoint': u'/dev/vdc', u'volume_id': 1}, u'_context_auth_token': u'07302338\
-e85e-49cf-a50c-c230a30ad637', u'_context_strategy': u'keystone', u'_context_is_admin': False, u'_context_project_id': u'2', u'_\
context_timestamp': u'2012-01-11T19:41:58.186031', u'_context_user_id': u'demo', u'method': u'attach_volume', u'_context_remote_\
address': u'172.18.0.146'} from (pid=8603) __call__ /opt/stack/nova/nova/rpc/impl_kombu.py:629
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,268 INFO nova.api.openstack.wsgi [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] htt\
p://172.18.0.146:8774/v1.1/2/servers/3d37d21e-8fba-46a4-a0e1-d137f1d17597/os-volume_attachments returned with HTTP 200
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,268 DEBUG nova.rpc [-] unpacked context: {'user_id': u'demo', 'roles': [u'Member',\
 u'sysadmin', u'netadmin'], 'timestamp': u'2012-01-11T19:41:58.186031', 'auth_token': u'07302338-e85e-49cf-a50c-c230a30ad637', '\
msg_id': None, 'remote_address': u'172.18.0.146', 'strategy': u'keystone', 'is_admin': False, 'request_id': u'229ab0dc-3085-4f4c\
-bb80-d8104c96bef8', 'project_id': u'2', 'read_deleted': u'no'} from (pid=8603) _unpack_context /opt/stack/nova/nova/rpc/impl_ko\
mbu.py:675
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,269 INFO nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] check_\
instance_lock: decorating: |<function attach_volume at 0x3393ed8>|
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,269 INFO nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] check_\
instance_lock: arguments: |<nova.compute.manager.ComputeManager object at 0x31a96d0>| |<nova.rpc.impl_kombu.RpcContext object at\
 0x4a51fd0>| |3d37d21e-8fba-46a4-a0e1-d137f1d17597|
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,270 DEBUG nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] insta\
nce 3d37d21e-8fba-46a4-a0e1-d137f1d17597: getting locked state from (pid=8603) get_lock /opt/stack/nova/nova/compute/manager.py:\
1426
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,320 INFO nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] check_\
instance_lock: locked: |False|
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,320 INFO nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] check_\
instance_lock: admin: |False|
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,320 INFO nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] check_\
instance_lock: executing: |<function attach_volume at 0x3393ed8>|
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,368 AUDIT nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] insta\
nce 3d37d21e-8fba-46a4-a0e1-d137f1d17597: attaching volume 1 to /dev/vdc
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,388 DEBUG nova.rpc [-] Making asynchronous call on volume.xg06 ... from (pid=8603)\
 multicall /opt/stack/nova/nova/rpc/impl_kombu.py:759
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,388 DEBUG nova.rpc [-] MSG_ID is e23a4350fc494265ad48fde056b02613 from (pid=8603) \
multicall /opt/stack/nova/nova/rpc/impl_kombu.py:762
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,395 DEBUG nova.rpc [-] received {u'_context_roles': [u'Member', u'sysadmin', u'net\
admin'], u'_msg_id': u'e23a4350fc494265ad48fde056b02613', u'_context_read_deleted': u'no', u'_context_request_id': u'229ab0dc-30\
85-4f4c-bb80-d8104c96bef8', u'args': {u'volume_id': 1, u'address': u'172.18.0.146'}, u'_context_auth_token': u'07302338-e85e-49c\
f-a50c-c230a30ad637', u'_context_strategy': u'keystone', u'_context_is_admin': True, u'_context_project_id': u'2', u'_context_ti\
mestamp': u'2012-01-11T19:41:58.186031', u'_context_user_id': u'demo', u'method': u'initialize_connection', u'_context_remote_ad\
dress': u'172.18.0.146'} from (pid=8709) __call__ /opt/stack/nova/nova/rpc/impl_kombu.py:629
Jan 11 14:41:58 xg06eth0  2012-01-11 14:41:58,396 DEBUG nova.rpc [-] unpacked context: {'user_id': u'demo', 'roles': [u'Member',\
 u'sysadmin', u'netadmin'], 'timestamp': u'2012-01-11T19:41:58.186031', 'auth_token': u'07302338-e85e-49cf-a50c-c230a30ad637', '\
msg_id': u'e23a4350fc494265ad48fde056b02613', 'remote_address': u'172.18.0.146', 'strategy': u'keystone', 'is_admin': True, 'req\
uest_id': u'229ab0dc-3085-4f4c-bb80-d8104c96bef8', 'project_id': u'2', 'read_deleted': u'no'} from (pid=8709) _unpack_context /o\
pt/stack/nova/nova/rpc/impl_kombu.py:675
Jan 11 14:41:59 xg06eth0  2012-01-11 14:41:59,288 DEBUG nova.utils [-] Running cmd (subprocess): sudo iscsiadm -m node -T iqn.20\
10-10.org.openstack:volume-00000001 -p 172.18.0.146:3260 from (pid=8603) execute /opt/stack/nova/nova/utils.py:199
Jan 11 14:41:59 xg06eth0 2012-01-11 14:41:59,303 DEBUG nova.virt.libvirt.volume [-] iscsiadm (): stdout=# BEGIN RECORD 2.0-871#0\
12node.name = iqn.2010-10.org.openstack:volume-00000001#012node.tpgt = -1#012node.startup = automatic#012iface.hwaddress = <empt\
y>#012iface.ipaddress = <empty>#012iface.iscsi_ifacename = default#012iface.net_ifacename = <empty>#012iface.transport_name = tc\
p#012iface.initiatorname = <empty>#012node.discovery_address = <empty>#012node.discovery_port = 0#012node.discovery_type = stati\
c#012node.session.initial_cmdsn = 0#012node.session.initial_login_retry_max = 8#012node.session.xmit_thread_priority = -20#012no\
de.session.cmds_max = 128#012node.session.queue_depth = 32#012node.session.auth.authmethod = None#012node.session.auth.username \
= <empty>#012node.session.auth.password = <empty>#012node.session.auth.username_in = <empty>#012node.session.auth.password_in = \
<empty>#012node.session.timeo.replacement_timeout = 120#012node.session.err_timeo.abort_timeout = 15#012node.session.err_timeo.l\
u_reset_timeout = 20#012node.session.err_timeo.host_reset_timeout = 60#012node.session.iscsi.FastAbort = Yes#012node.session.isc\
si.InitialR2T = No#012node.session.iscsi.ImmediateData = Yes#012node.session.iscsi.FirstBurstLength = 262144#012node.session.isc\
si.MaxBurstLength = 16776192#012node.session.iscsi.DefaultTime2Retain = 0#012node.session.iscsi.DefaultTime2Wait = 2#012node.ses\
sion.iscsi.MaxConnections = 1#012node.session.iscsi.MaxOutstandingR2T = 1#012node.session.iscsi.ERL = 0#012node.conn[0].address \
= 172.18.0.146#012node.conn[0].port = 3260#012node.conn[0].startup = manual#012node.conn[0].tcp.window_size = 524288#012node.con\
n[0].tcp.type_of_service = 0#012node.conn[0].timeo.logout_timeout = 15#012node.conn[0].timeo.login_timeout = 15#012node.conn[0].\
timeo.auth_timeout = 45#012node.conn[0].timeo.noop_out_interval = 5#012node.conn[0].timeo.noop_out_timeout = 5#012node.conn[0].i\
scsi.MaxRecvDataSegmentLength = 262144#012node.conn[0].iscsi.HeaderDigest = None#012node.conn[0].iscsi.DataDigest = None#012node\
.conn[0].iscsi.IFM
Jan 11 14:41:59 xg06eth0  2012-01-11 14:41:59,305 DEBUG nova.utils [-] Running cmd (subprocess): sudo iscsiadm -m node -T iqn.20\
10-10.org.openstack:volume-00000001 -p 172.18.0.146:3260 --login from (pid=8603) execute /opt/stack/nova/nova/utils.py:199
Jan 11 14:41:59 xg06eth0  2012-01-11 14:41:59,319 DEBUG nova.utils [-] Result was 255 from (pid=8603) execute /opt/stack/nova/no\
va/utils.py:215
Jan 11 14:41:59 xg06eth0  2012-01-11 14:41:59,320 ERROR nova.compute.manager [229ab0dc-3085-4f4c-bb80-d8104c96bef8 demo 2] insta\
nce 3d37d21e-8fba-46a4-a0e1-d137f1d17597: attach failed /dev/vdc, removing#012(nova.compute.manager): TRACE: Traceback (most rec\
ent call last):#012(nova.compute.manager): TRACE:   File "/opt/stack/nova/nova/compute/manager.py", line 1529, in attach_volume#\
012(nova.compute.manager): TRACE:     mountpoint)#012(nova.compute.manager): TRACE:   File "/opt/stack/nova/nova/exception.py", \
line 130, in wrapped#012(nova.compute.manager): TRACE:     return f(*args, **kw)#012(nova.compute.manager): TRACE:   File "/opt/\
stack/nova/nova/virt/libvirt/connection.py", line 427, in attach_volume#012(nova.compute.manager): TRACE:     mount_device)#012(\
nova.compute.manager): TRACE:   File "/opt/stack/nova/nova/virt/libvirt/connection.py", line 419, in volume_driver_method#012(no\
va.compute.manager): TRACE:     return method(connection_info, *args, **kwargs)#012(nova.compute.manager): TRACE:   File "/opt/s\
tack/nova/nova/virt/libvirt/volume.py", line 128, in connect_volume#012(nova.compute.manager): TRACE:     self._run_iscsiadm(isc\
si_properties, ("--login",))#012(nova.compute.manager): TRACE:   File "/opt/stack/nova/nova/virt/libvirt/volume.py", line 96, in\
 _run_iscsiadm#012(nova.compute.manager): TRACE:     check_exit_code=check_exit_code)#012(nova.compute.manager): TRACE:   File "\
/opt/stack/nova/nova/utils.py", line 223, in execute#012(nova.compute.manager): TRACE:     cmd=' '.join(cmd))#012(nova.compute.m\
anager): TRACE: ProcessExecutionError: Unexpected error while running command.#012(nova.compute.manager): TRACE: Command: sudo i\
scsiadm -m node -T iqn.2010-10.org.openstack:volume-00000001 -p 172.18.0.146:3260 --login#012(nova.compute.manager): TRACE: Exit\
 code: 255#012(nova.compute.manager): TRACE: Stdout: 'Logging in to [iface: default, target: iqn.2010-10.org.openstack:volume-00\
000001, portal: 172.18.0.146,3260]\n'#012(nova.compute.manager): TRACE: Stderr: 'iscsiadm: Could not login to [iface: default, t\
arget: iqn.2010-
Jan 11 14:41:59 xg06eth0  2012-01-11 14:41:59,351 DEBUG nova.rpc [-] Making asynchronous call on volume.xg06 ... from (pid=8603)\
 multicall /opt/stack/nova/nova/rpc/impl_kombu.py:759
-UUU:----F1  syslog         99% L??    (Fundamental)---------------------------------------------------------------------------