Dell EMC Unity driver

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.


Software Version
Unity OE 4.1.X
OpenStack Ocata
storops 0.4.15 or newer

Supported operations

  • Create, delete, attach, and detach 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.

Driver configuration


The following instructions should all be performed on Black 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.

    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 Dell EMC Unity volume driver configuration options
Configuration option = Default value Description
unity_io_ports = None (List) A comma-separated list of iSCSI or FC ports to be used. Each port can be Unix-style glob expressions.
unity_storage_pool_names = None (List) 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

Only thin volume provisioning is supported in Unity volume driver.

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.


Set backup_use_same_host to true to enable the efficient backup.


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 [request_id] 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
[request_id]Return request ID to caller
Creative Commons Attribution 3.0 License

Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.