Dell EMC Unity driver

Unity driver has been integrated in the OpenStack Block Storage project since the Ocata release. The driver is built on the top of Block Storage framework and a Dell EMC distributed Python package storops.




Unity OE

4.1.X or newer


1.1.0 or newer

Supported operations

  • Create, delete, attach, and detach volumes.

  • Create, delete, attach, and detach compressed volumes.

  • Create, list, and delete volume snapshots.

  • Create a volume from a snapshot.

  • Copy an image to a volume.

  • Create an image from a volume.

  • Clone a volume.

  • Extend a volume.

  • Migrate a volume.

  • Get volume statistics.

  • Efficient non-disruptive volume backup.

  • Revert a volume to a snapshot.

  • Create thick volumes.

  • Create and delete consistent groups.

  • Add/remove volumes to/from a consistent group.

  • Create and delete consistent group snapshots.

  • Clone a consistent group.

  • Create a consistent group from a snapshot.

  • Attach a volume to multiple servers simultaneously (multiattach).

  • Volume replications.

Driver configuration


The following instructions should all be performed on Block Storage nodes.

  1. Install storops from pypi:

    # pip install storops
  2. Add the following content into /etc/cinder/cinder.conf:

    enabled_backends = unity
    # Storage protocol
    storage_protocol = iSCSI
    # Unisphere IP
    san_ip = <SAN IP>
    # Unisphere username and password
    san_login = <SAN LOGIN>
    san_password = <SAN PASSWORD>
    # Volume driver name
    volume_driver = cinder.volume.drivers.dell_emc.unity.Driver
    # backend's name
    volume_backend_name = Storage_ISCSI_01


    These are minimal options for Unity driver, for more options, see Driver options.


(Optional) If you require multipath based data access, perform below steps on both Block Storage and Compute nodes.

  1. Install sysfsutils, sg3-utils and multipath-tools:

    # apt-get install multipath-tools sg3-utils sysfsutils
  2. (Required for FC driver in case Auto-zoning Support is disabled) Zone the FC ports of Compute nodes with Unity FC target ports.

  3. Enable Unity storage optimized multipath configuration:

    Add the following content into /etc/multipath.conf

    blacklist {
        # Skip the files uner /dev that are definitely not FC/iSCSI devices
        # Different system may need different customization
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^hd[a-z][0-9]*"
        devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]"
        # Skip LUNZ device from VNX/Unity
        device {
            vendor "DGC"
            product "LUNZ"
    defaults {
        user_friendly_names no
        flush_on_last_del yes
    devices {
        # Device attributed for EMC CLARiiON and VNX/Unity series ALUA
        device {
            vendor "DGC"
            product ".*"
            product_blacklist "LUNZ"
            path_grouping_policy group_by_prio
            path_selector "round-robin 0"
            path_checker emc_clariion
            features "0"
            no_path_retry 12
            hardware_handler "1 alua"
            prio alua
            failback immediate
  4. Restart the multipath service:

    # service multipath-tools restart
  5. Enable multipath for image transfer in /etc/cinder/cinder.conf for each backend or in [backend_defaults] section as a common configuration for all backends.

    use_multipath_for_image_xfer = True

    Restart the cinder-volume service to load the change.

  6. Enable multipath for volume attache/detach in /etc/nova/nova.conf.

    volume_use_multipath = True
  7. Restart the nova-compute service.

Driver options

Description of Unity configuration options

Configuration option = Default value


remove_empty_host = False

(Boolean) To remove the host from Unity when the last LUN is detached from it. By default, it is False.

san_api_port = None

(Port(min=0, max=65535)) Port to use to access the SAN API

san_clustername = <>

(String) Cluster name to use for creating volumes

san_ip = <>

(String) IP address of SAN controller

san_is_local = False

(Boolean) Execute commands locally instead of over SSH; use if the volume service is running on the SAN device

san_login = admin

(String) Username for SAN controller

san_password = <>

(String) Password for SAN controller

san_private_key = <>

(String) Filename of private key to use for SSH authentication

san_ssh_port = 22

(Port(min=0, max=65535)) SSH port to use with SAN

san_thin_provision = True

(Boolean) Use thin provisioning for SAN volumes?

ssh_conn_timeout = 30

(Integer) SSH connection timeout in seconds

ssh_max_pool_conn = 5

(Integer) Maximum ssh connections in the pool

ssh_min_pool_conn = 1

(Integer) Minimum ssh connections in the pool

unity_io_ports = []

(List of String) A comma-separated list of iSCSI or FC ports to be used. Each port can be Unix-style glob expressions.

unity_storage_pool_names = []

(List of String) A comma-separated list of storage pool names to be used.

FC or iSCSI ports option

Specify the list of FC or iSCSI ports to be used to perform the IO. Wild card character is supported. For iSCSI ports, use the following format:

unity_io_ports = spa_eth2, spb_eth2, *_eth3

For FC ports, use the following format:

unity_io_ports = spa_iom_0_fc0, spb_iom_0_fc0, *_iom_0_fc1

List the port ID with the uemcli command:

$ uemcli /net/port/eth show -output csv
"spa_eth2","SP A Ethernet Port 2","spa","file, net, iscsi", ...
"spb_eth2","SP B Ethernet Port 2","spb","file, net, iscsi", ...

$ uemcli /net/port/fc show -output csv
"spa_iom_0_fc0","SP A I/O Module 0 FC Port 0","spa", ...
"spb_iom_0_fc0","SP B I/O Module 0 FC Port 0","spb", ...

Live migration integration

It is suggested to have multipath configured on Compute nodes for robust data access in VM instances live migration scenario. Once user_friendly_names no is set in defaults section of /etc/multipath.conf, Compute nodes will use the WWID as the alias for the multipath devices.

To enable multipath in live migration:


Make sure Driver configuration steps are performed before following steps.

  1. Set multipath in /etc/nova/nova.conf:

    volume_use_multipath = True

    Restart nova-compute service.

  2. Set user_friendly_names no in /etc/multipath.conf

    defaults {
        user_friendly_names no
  3. Restart the multipath-tools service.

Thin and thick provisioning

By default, the volume created by Unity driver is thin provisioned. Run the following commands to create a thick volume.

# openstack volume type create --property provisioning:type=thick \
  --property thick_provisioning_support='<is> True' thick_volume_type
# openstack volume create --type thick_volume_type thick_volume

Compressed volume support

Unity driver supports compressed volume creation, modification and deletion. In order to create a compressed volume, a volume type which enables compression support needs to be created first:

$ openstack volume type create CompressedVolumeType
$ openstack volume type set --property provisioning:type=compressed --property compression_support='<is> True' CompressedVolumeType

Then create volume and specify the new created volume type.


In Unity, only All-Flash pools support compressed volume, for the other type of pools, “‘compression_support’: False” will be returned when getting pool stats.

Storage-assisted volume migration support

Unity driver supports storage-assisted volume migration, when the user starts migrating with cinder migrate --force-host-copy False <volume_id> <host> or cinder migrate <volume_id> <host>, cinder will try to leverage the Unity’s native volume migration functionality. If Unity fails to migrate the volume, host-assisted migration will be triggered.

In the following scenarios, Unity storage-assisted volume migration will not be triggered. Instead, host-assisted volume migration will be triggered:

  • Volume is to be migrated across backends.

  • Migration of cloned volume. For example, if vol_2 was cloned from vol_1, the storage-assisted volume migration of vol_2 will not be triggered.

QoS support

Unity driver supports maxBWS and maxIOPS specs for the back-end consumer type. maxBWS represents the Maximum IO/S absolute limit, maxIOPS represents the Maximum Bandwidth (KBPS) absolute limit on the Unity respectively.

Auto-zoning support

Unity volume driver supports auto-zoning, and share the same configuration guide for other vendors. Refer to Fibre Channel Zone Manager for detailed configuration steps.

Solution for LUNZ device

The EMC host team also found LUNZ on all of the hosts, EMC best practice is to present a LUN with HLU 0 to clear any LUNZ devices as they can cause issues on the host. See KB LUNZ Device.

To workaround this issue, Unity driver creates a Dummy LUN (if not present), and adds it to each host to occupy the HLU 0 during volume attachment.


This Dummy LUN is shared among all hosts connected to the Unity.

Efficient non-disruptive volume backup

The default implementation in Block Storage for non-disruptive volume backup is not efficient since a cloned volume will be created during backup.

An effective approach to backups is to create a snapshot for the volume and connect this snapshot to the Block Storage host for volume backup.

SSL support

Admin is able to enable the SSL verification for any communication against Unity REST API.

By default, the SSL verification is disabled, user can enable it by following steps:

  1. Setup the Unity array certificate and import it to the Unity, see section Storage system certificate of Security Configuration Guide.

  2. Import the CA certficate to the Cinder nodes on which the driver is running.

  3. Enable the changes on cinder nodes and restart the cinder services.

driver_ssl_cert_verify = True
driver_ssl_cert_path = <path to the CA>

If driver_ssl_cert_path is omitted, the system default CA will be used for CA verification.

IPv6 support

This driver can support IPv6-based control path and data path.

For control path, please follow below steps:

  • Enable Unity’s Unipshere IPv6 address.

  • Configure the IPv6 network to make sure that cinder node can access Unishpere via IPv6 address.

  • Change Cinder config file /etc/cinder/cinder.conf. Make the san_ip as Unisphere IPv6 address. For example, san_ip = [fd99:f17b:37d0::100].

  • Restart the Cinder service to make new configuration take effect.

Note: The IPv6 support on control path depends on the fix of cpython bug 32185. Please make sure your Python’s version includes this bug’s fix.

For data path, please follow below steps:

  • On Unity, Create iSCSI interface with IPv6 address.

  • Configure the IPv6 network to make sure that you can ping the Unity’s iSCSI IPv6 address from the Cinder node.

  • If you create a volume using Cinder and attach it to a VM, the connection between this VM and volume will be IPv6-based iSCSI.

Force detach volume from all hosts

The user could use os-force_detach action to detach a volume from all its attached hosts. For more detail, please refer to

Consistent group support

For a group to support consistent group snapshot, the group specs in the corresponding group type should have the following entry:

{'consistent_group_snapshot_enabled': <is> True}

Similarly, for a volume to be in a group that supports consistent group snapshots, the volume type extra specs would also have the following entry:

{'consistent_group_snapshot_enabled': <is> True}

Refer to Generic volume groups for command lines detail.

Volume replications

To enable volume replications, follow below steps:

  1. On Unisphere, configure remote system and interfaces for replications.

The way could be different depending on the type of replications - sync or async. Refer to Unity Replication White Paper for more detail.

  1. Add replication_device to storage backend settings in cinder.conf, then restart Cinder Volume service.

    Example of cinder.conf for volume replications:

    san_ip =
    replication_device = backend_id:unity-secondary,san_ip:yyy.yyy.yyy.yyy,san_password:****,max_time_out_of_sync:60
    • Only one replication_device can be configured for each primary backend.

    • Keys backend_id, san_ip, san_password, and max_time_out_of_sync are supported in replication_device, while backend_id and san_ip are required.

    • san_password uses the same one as primary backend’s if it is omitted.

    • max_time_out_of_sync is the max time in minutes replications are out of sync. It must be equal or greater than 0. 0 means sync replications of volumes will be created. Note that remote systems for sync replications need to be created on Unity first. 60 will be used if it is omitted.

  2. Create a volume type with property replication_enabled=’<is> True’.

    $ openstack volume type create --property replication_enabled='<is> True' type-replication
  3. Any volumes with volume type of step #3 will failover to secondary backend after failover_host is executed.

    $ cinder failover-host --backend_id unity-secondary stein@unity-primary
  4. Later, they could be failed back.

    $ cinder failover-host --backend_id default stein@unity-primary


The volume can be deleted even when it is participating in a replication. The replication session will be deleted from Unity before the LUN is deleted.


To troubleshoot a failure in OpenStack deployment, the best way is to enable verbose and debug log, at the same time, leverage the build-in Return request ID to caller to track specific Block Storage command logs.

  1. Enable verbose log, set following in /etc/cinder/cinder.conf and restart all Block Storage services:

    debug = True
    verbose = True

    If other projects (usually Compute) are also involved, set debug and verbose to True.

  2. use --debug to trigger any problematic Block Storage operation:

    # cinder --debug create --name unity_vol1 100

    You will see the request ID from the console, for example:

    DEBUG:keystoneauth:REQ: curl -g -i -X POST -H
    "User-Agent: python-cinderclient" -H "Content-Type: application/json" -H
    "Accept: application/json" -H "X-Auth-Token:
    {SHA1}bf4a85ad64302b67a39ad7c6f695a9630f39ab0e" -d '{"volume": {"status":
    "creating", "user_id": null, "name": "unity_vol1", "imageRef": null,
    "availability_zone": null, "description": null, "multiattach": false,
    "attach_status": "detached", "volume_type": null, "metadata": {},
    "consistencygroup_id": null, "source_volid": null, "snapshot_id": null,
    "project_id": null, "source_replica": null, "size": 10}}'
    DEBUG:keystoneauth:RESP: [202] X-Compute-Request-Id:
    req-3a459e0e-871a-49f9-9796-b63cc48b5015 Content-Type: application/json
    Content-Length: 804 X-Openstack-Request-Id:
    req-3a459e0e-871a-49f9-9796-b63cc48b5015 Date: Mon, 12 Dec 2016 09:31:44 GMT
    Connection: keep-alive
  3. Use commands like grep, awk to find the error related to the Block Storage operations.

    # grep "req-3a459e0e-871a-49f9-9796-b63cc48b5015" cinder-volume.log