Replication in OpenStack¶

Replication provides a Disaster Recovery (DR) solution for mission-critical workloads. This guide will provide you step by step procedure on how to configure/utilize the Cinder Replication feature in your own deployment. There are two parts to the feature, Cinder side and Driver side. The Cinder side steps should be common, however, the driver side steps may differ. This guide will use RBD as the reference driver for the procedure.

Prerequisites¶

Should have 2 backend clusters
Cinder driver should support replication

See Cinder Driver Support Matrix to know about which backends support replication.

Enable Replication¶

CEPH¶

Reference: https://docs.ceph.com/en/latest/rbd/rbd-mirroring

NOTE: These steps are Ceph specific and are tested against Pacific release of Ceph. Make sure that:

A pool with the same name exists on both storage clusters.
A pool contains journal-enabled images you want to mirror.

STEPS¶

Get shell access for primary and secondary ceph clusters

site-a # sudo cephadm shell --fsid <PRIMARY_FSID> -c /etc/ceph/ceph.conf -k /etc/ceph/ceph.client.admin.keyring
site-b # sudo cephadm shell --fsid <SECONDARY_FSID> -c /etc/ceph2/ceph.conf -k /etc/ceph2/ceph.client.admin.keyring

Enable RBD mirroring on both hosts

site-a # ceph orch apply rbd-mirror --placement=<Primary Host>
site-b # ceph orch apply rbd-mirror --placement=<Secondary Host>

Enable image level mirroring

site-a # rbd mirror pool enable volumes image
site-b # rbd mirror pool enable volumes image

Bootstrap Peers

NOTE: These commands needs to be executed outside the cephadm shell.

site-a # sudo cephadm shell --fsid <PRIMARY_FSID> -c /etc/ceph/ceph.conf -k /etc/ceph/ceph.client.admin.keyring -- rbd mirror pool peer bootstrap create --site-name <FSID of site-a> <pool_name> | awk 'END{print}' > "$HOME/token_file"
site-b # sudo cephadm shell --fsid <SECONDARY_FSID> -c /etc/ceph2/ceph.conf -k /etc/ceph2/ceph.client.admin.keyring -- rbd mirror pool peer bootstrap import --site-name <FSID of site-b> <pool_name> - < "$HOME/token_file"

Verification¶

Verify that Mode: image and Direction: rx-tx are set in the below output.

site-a # rbd mirror pool info volumes

Mode: image
Site Name: 55b6325e-e6b3-4b7c-91fd-64b5720c1685

Peer Sites:

UUID: 544777e2-4418-4dba-8f10-03238f63990d
Name: 69cc3310-8dd4-4656-a75b-64d4890b0ca6
Mirror UUID:
Direction: rx-tx
Client: client.rbd-mirror-peer

site-b # rbd mirror pool info volumes

Mode: image
Site Name: 69cc3310-8dd4-4656-a75b-64d4890b0ca6

Peer Sites:

UUID: a102dd15-cc37-4df6-acf1-266ec0248a37
Name: 55b6325e-e6b3-4b7c-91fd-64b5720c1685
Mirror UUID:
Direction: rx-tx
Client: client.rbd-mirror-peer

CINDER¶

STEPS¶

Set the replication_device values in cinder.conf file.

replication_device = backend_id:<unique_identifier>,conf:<ceph.conf path for site-b>,user:<user for site-b>,secret_uuid: <libvirt secret UUID>

Create a replicated volume type. Note that we’ve used the volume_backend_name=ceph here which can be different for your deployment.

openstack volume type create --property replication_enabled='<is> True' --property volume_backend_name='ceph' ceph

Verification¶

Create a volume with replicated volume type

openstack volume create --type ceph --size 1 replicated-volume

Confirm on RBD side that a replica is created

On site-a, you will see mirroring primary: true

site-a # rbd info volumes/volume-d217e292-0a98-4572-ae68-a4c40b73a278

rbd image 'volume-d217e292-0a98-4572-ae68-a4c40b73a278':
        size 1 GiB in 256 objects
        order 22 (4 MiB objects)
        snapshot_count: 0
        id: a9ebeef62570
        block_name_prefix: rbd_data.a9ebeef62570
        format: 2
        features: layering, exclusive-lock, object-map, fast-diff, deep-flatten, journaling
        op_features:
        flags:
        create_timestamp: Thu May 15 14:15:04 2025
        access_timestamp: Thu May 15 14:15:04 2025
        modify_timestamp: Thu May 15 14:15:04 2025
        journal: a9ebeef62570
        mirroring state: enabled
        mirroring mode: journal
        mirroring global id: e8f583ed-abab-489c-b9d5-ef68c0a1b56f
        mirroring primary: true

On site-b, you will see mirroring primary: false

rbd ls volumes
volume-d217e292-0a98-4572-ae68-a4c40b73a278

rbd info volumes/volume-d217e292-0a98-4572-ae68-a4c40b73a278
rbd image 'volume-d217e292-0a98-4572-ae68-a4c40b73a278':
        size 1 GiB in 256 objects
        order 22 (4 MiB objects)
        snapshot_count: 0
        id: 6a993924cde
        block_name_prefix: rbd_data.6a993924cde
        format: 2
        features: layering, exclusive-lock, object-map, fast-diff, deep-flatten, journaling
        op_features:
        flags:
        create_timestamp: Thu May 15 14:15:06 2025
        access_timestamp: Thu May 15 14:15:06 2025
        modify_timestamp: Thu May 15 14:15:06 2025
        journal: 6a993924cde
        mirroring state: enabled
        mirroring mode: journal
        mirroring global id: e8f583ed-abab-489c-b9d5-ef68c0a1b56f
        mirroring primary: false

Failover of a Boot From Volume (BFV) Server¶

Create a bootable replicated volume

openstack volume create --type ceph --image <Image-UUID> --size 1 test-bootable-replicated

Launch a server from the volume

openstack server create --flavor c1 --nic=none --volume <Volume-UUID> test-bfv-server

Create a file to write data to the VM disk

$ cat > failover-dr <<EOF
> # Before failover
> this should be consistent before/after failover
> EOF

Failover the replicated cinder backend

cinder failover-host <host>@<backend>

Shelve/unshelve the server. (This is required to remove the connection from the volume in primary backend and create a new connection to the volume replica in secondary backend)

openstack server shelve <server-UUID>
openstack server unshelve <server-UUID>

Verification¶

Verify that the connection is now made from secondary cluster

# In cinder-volume logs, we can see the ``hosts``, ``cluster_name`` and ``auth_username`` fields will point to secondary cluster
Connection info returned from driver {'name': 'volumes/volume-e310359c-6587-4454-9a9c-a590b50dd4a5', 'hosts': ['127.0.0.1'], 'ports': ['6789'], 'cluster_name': 'ceph2', 'auth_enabled': True, 'auth_username': 'cinder2', 'secret_type': '***', 'secret_uuid': '***', 'volume_id': 'e310359c-6587-4454-9a9c-a590b50dd4a5', 'discard': True, 'qos_specs': None, 'access_mode': 'rw', 'encrypted': False, 'cacheable': False, 'driver_volume_type': 'rbd', 'attachment_id': 'b691cd50-83a1-4484-8081-7120a5cad054', 'enforce_multipath': True}

Confirm that the data written before failover is persistent.

$ cat failover-dr
# Before failover
this should be consistent before/after failover

Failback of a Boot From Volume (BFV) Server¶

Create a file and write data to the VM disk. (Note that the volume backend is in failover mode and we are writing to the replica disk in secondary backend.)

$ cat > failover-dr <<EOF
> # Before Failback
> this should be consistent before/after failback
> EOF

Failback to primary backend

cinder failover-host <host>@<backend> --backend_id default

Shelve/Unshelve the server (This is required to remove the connection from the replica volume in secondary backend and create a new connection to the original volume in primary backend)

openstack server shelve <server UUID>
openstack server unshelve <server UUID>

Verification¶

Verify that the connection is now made from primary cluster

# In cinder-volume logs, we can see the ``hosts``, ``cluster_name`` and ``auth_username`` fields will point to primary cluster
Connection info returned from driver {'name': 'volumes/volume-e310359c-6587-4454-9a9c-a590b50dd4a5', 'hosts': ['10.0.79.218'], 'ports': ['6789'], 'cluster_name': 'ceph', 'auth_enabled': True, 'auth_username': 'cinder', 'secret_type': '***', 'secret_uuid': '***', 'volume_id': 'e310359c-6587-4454-9a9c-a590b50dd4a5', 'discard': True, 'qos_specs': None, 'access_mode': 'rw', 'encrypted': False, 'cacheable': False, 'driver_volume_type': 'rbd', 'attachment_id': '2c8bb96b-5d5c-444c-aba5-13272b673b34', 'enforce_multipath': True}

Confirm that the data written before failback is persistent.

$ cat failback-dr
# Before Failback
this should be consistent before/after failback

Failover of a External Data Volume¶

Create a test server

openstack server create --flavor c1 --nic=none --image <Image UUID> test-server

Create and attach data volume to it

openstack volume create --type ceph --size 1 replicated-vol
openstack server add volume <Server UUID> <Volume UUID>

Write data to the volume. Note that creating a filesystem and mounting the device are implied here.

$ cat > failover-dr <<EOF
> # Before failover
> this should be consistent before/after failover
> EOF

Detach and attach the external data volume

openstack server remove volume <Server UUID> <Volume UUID>
openstack server add volume <Server UUID> <Volume UUID>

Verification¶

Verify that the connection is now made from secondary cluster

# In cinder-volume logs, we can see the ``hosts``, ``cluster_name`` and ``auth_username`` fields will point to secondary cluster
Connection info returned from driver {'name': 'volumes/volume-437573fd-08e2-42c9-b658-2f982bc0cdd2', 'hosts': ['127.0.0.1'], 'ports': ['6789'], 'cluster_name': 'ceph2', 'auth_enabled': True, 'auth_username': 'cinder2', 'secret_type': '***', 'secret_uuid': '***', 'volume_id': '437573fd-08e2-42c9-b658-2f982bc0cdd2', 'discard': True, 'qos_specs': None, 'access_mode': 'rw', 'encrypted': False, 'cacheable': False, 'driver_volume_type': 'rbd', 'attachment_id': '595bd265-4212-4d9a-8d48-ba6fb59d19fe', 'enforce_multipath': True}

Verify that the data exists after failover. NOTE that in some cases, the data might/might not be persistent depending on the type of replication i.e. async or sync.

$ cat failover-dr
# Before failover
this should be consistent before/after failover

Failback of a External Data Volume¶

Create a file and write data to the external data volume. (Note that the volume backend is in failover mode and we are writing to the replica disk in secondary backend.)

$ cat > failback-dr <<EOF
> # Before Failback
> this should be consistent before/after failback
> EOF

Failback to primary backend

cinder failover-host <host>@<backend> --backend_id default

Detach and attach the external data volume

openstack server remove volume <Server UUID> <Volume UUID>
openstack server add volume <Server UUID> <Volume UUID>

Verification¶

Verify that the connection is now made from primary cluster

# In cinder-volume logs, we can see the ``hosts``, ``cluster_name`` and ``auth_username`` fields will point to primary cluster
Connection info returned from driver {'name': 'volumes/volume-437573fd-08e2-42c9-b658-2f982bc0cdd2', 'hosts': ['10.0.79.218'], 'ports': ['6789'], 'cluster_name': 'ceph', 'auth_enabled': True, 'auth_username': 'cinder', 'secret_type': '***', 'secret_uuid': '***', 'volume_id': '437573fd-08e2-42c9-b658-2f982bc0cdd2', 'discard': True, 'qos_specs': None, 'access_mode': 'rw', 'encrypted': False, 'cacheable': False, 'driver_volume_type': 'rbd', 'attachment_id': 'b4e0c0a6-50b6-4ff3-83a5-a3da7be0e18c', 'enforce_multipath': True}

Confirm that the data written before failback is persistent. NOTE that in some cases, the data might/might not be persistent depending on the type of replication i.e. async or sync.

$ cat failback-dr
# Before Failback
this should be consistent before/after failback

Replication in OpenStack

Replication in OpenStack¶

Prerequisites¶

Enable Replication¶

CEPH¶

STEPS¶

Verification¶

CINDER¶

STEPS¶

Verification¶

Failover of a Boot From Volume (BFV) Server¶

Verification¶

Failback of a Boot From Volume (BFV) Server¶

Verification¶

Failover of a External Data Volume¶

Verification¶

Failback of a External Data Volume¶

Verification¶

cinder 26.1.0.dev81

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