Open Stack

Hi, I'm trying to use lvm thin provisioning with openstack cinder (mitaka)
but I have a problem with snapshots. I'm trying to create a snapshot from a
volume (detached) and then create a new volume from the snapshot.

1) Snapshot creation works well and I have (with lvs)

  LV                                             VG              Attr
LSize  Pool                 Origin
Data%  Meta%  Move Log Cpy%Sync Convert
  *_snapshot-f702a3b0-e021-471b-80c3-56cab0c1c1e6 cinder-volumes2
Vwi---tz-k  1.00g cinder-volumes2-pool
volume-a60699c5-55c2-4dbc-b74a-64b51f2f4dd2*

  activationvol                                  cinder-volumes2 -wi-a-----
16.00m

  cinder-volumes2-pool                           cinder-volumes2 twi-aotz--
18.98g
0.00   0.59
  *volume-a60699c5-55c2-4dbc-b74a-64b51f2f4dd2    cinder-volumes2
Vwi-a-tz--  1.00g
cinder-volumes2-pool                                             0.00*


2) When I try to create the new volume from the snapshot I have an error:
/bin/dd: failed to open
/dev/mapper/cinder--volumes2-_snapshot--f702a3b0--e021--471b--80c3--56cab0c1c1e6\xe2\x80\x99:
No such file or directory\n'
But the new logical volume is created in the pool:

[root at mitaka-cinder-volume1-env3 ~]# lvs
  LV                                             VG              Attr
LSize  Pool                 Origin
Data%  Meta%  Move Log Cpy%Sync Convert
  _snapshot-f702a3b0-e021-471b-80c3-56cab0c1c1e6 cinder-volumes2
Vwi---tz-k  1.00g cinder-volumes2-pool
volume-a60699c5-55c2-4dbc-b74a-64b51f2f4dd2

  activationvol                                  cinder-volumes2 -wi-a-----
16.00m

  cinder-volumes2-pool                           cinder-volumes2 twi-aotz--
18.98g
0.00   0.59
  volume-86666116-660f-4bfc-a27e-fa5e689578ce    cinder-volumes2
Vwi-a-tz--  1.00g
cinder-volumes2-pool
0.00
  volume-a60699c5-55c2-4dbc-b74a-64b51f2f4dd2    cinder-volumes2
Vwi-a-tz--  1.00g
cinder-volumes2-pool
0.00


The problem is that in /dev/mapper I don't have the link associated with
the "snapshot" device. Is this a problem related to the operating system
configuration? Or I missing something in cinder.conf?? Should I modify some
setting in /etc/lvm/lvm.conf?

More details about my configuration:
[root at mitaka-cinder-volume1-env3 ~]# cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)
[root at mitaka-cinder-volume1-env3 ~]# rpm -qa | grep lvm
lvm2-libs-2.02.166-1.el7_3.1.x86_64
lvm2-2.02.166-1.el7_3.1.x86_64

My configuration in cinder.conf:

[lvm2]
volume_driver = cinder.volume.drivers.lvm.LVMVolumeDriver
volume_group = cinder-volumes2
volume_backend_name = LVM_iSCSI2
iscsi_protocol = iscsi
iscsi_helper = lioadm
iscsi_ip_address= 192.168.203.4
volume_clear=zero
volume_clear_size=30
lvm_type = thin
lvm_conf_file = /etc/cinder/lvm.conf <-- locking_type = 1, use_lvmetad = 0,
volume_list = [ "@pacemaker" ]   (I'm using an active/passive cluster with
an LVM resource for cinder-volumes2 VG)
max_over_subscription_ratio = 1.0


It seems that if I use thin provisioning the snapshot device doesn't exists
even though I see it with lvm so dd command fails.
I'm a bit confused. Any help will be really appreciated

Thank you
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