IBM Storwize family and SVC volume driver

IBM Storwize family and SVC volume driver

The volume management driver for Storwize family and SAN Volume Controller (SVC) provides OpenStack Compute instances with access to IBM Storwize family or SVC storage systems.

Supported operations

Storwize/SVC driver supports the following Block Storage service volume operations:

  • Create, list, delete, attach (map), and detach (unmap) volumes.
  • Create, list, and delete volume snapshots.
  • Copy an image to a volume.
  • Copy a volume to an image.
  • Clone a volume.
  • Extend a volume.
  • Retype a volume.
  • Create a volume from a snapshot.
  • Create, list, and delete consistency group.
  • Create, list, and delete consistency group snapshot.
  • Modify consistency group (add or remove volumes).
  • Create consistency group from source (source can be a CG or CG snapshot)
  • Manage an existing volume.
  • Failover-host for replicated back ends.
  • Failback-host for replicated back ends.

Configure the Storwize family and SVC system

Network configuration

The Storwize family or SVC system must be configured for iSCSI, Fibre Channel, or both.

If using iSCSI, each Storwize family or SVC node should have at least one iSCSI IP address. The IBM Storwize/SVC driver uses an iSCSI IP address associated with the volume’s preferred node (if available) to attach the volume to the instance, otherwise it uses the first available iSCSI IP address of the system. The driver obtains the iSCSI IP address directly from the storage system. You do not need to provide these iSCSI IP addresses directly to the driver.


If using iSCSI, ensure that the compute nodes have iSCSI network access to the Storwize family or SVC system.

If using Fibre Channel (FC), each Storwize family or SVC node should have at least one WWPN port configured. The driver uses all available WWPNs to attach the volume to the instance. The driver obtains the WWPNs directly from the storage system. You do not need to provide these WWPNs directly to the driver.


If using FC, ensure that the compute nodes have FC connectivity to the Storwize family or SVC system.

iSCSI CHAP authentication

If using iSCSI for data access and the storwize_svc_iscsi_chap_enabled is set to True, the driver will associate randomly-generated CHAP secrets with all hosts on the Storwize family system. The compute nodes use these secrets when creating iSCSI connections.


CHAP secrets are added to existing hosts as well as newly-created ones. If the CHAP option is enabled, hosts will not be able to access the storage without the generated secrets.


Not all OpenStack Compute drivers support CHAP authentication. Please check compatibility before using.


CHAP secrets are passed from OpenStack Block Storage to Compute in clear text. This communication should be secured to ensure that CHAP secrets are not discovered.

Configure storage pools

The IBM Storwize/SVC driver can allocate volumes in multiple pools. The pools should be created in advance and be provided to the driver using the storwize_svc_volpool_name configuration flag in the form of a comma-separated list. For the complete list of configuration flags, see Storwize family and SVC driver options in cinder.conf.

Configure user authentication for the driver

The driver requires access to the Storwize family or SVC system management interface. The driver communicates with the management using SSH. The driver should be provided with the Storwize family or SVC management IP using the san_ip flag, and the management port should be provided by the san_ssh_port flag. By default, the port value is configured to be port 22 (SSH). Also, you can set the secondary management IP using the storwize_san_secondary_ip flag.


Make sure the compute node running the cinder-volume management driver has SSH network access to the storage system.

To allow the driver to communicate with the Storwize family or SVC system, you must provide the driver with a user on the storage system. The driver has two authentication methods: password-based authentication and SSH key pair authentication. The user should have an Administrator role. It is suggested to create a new user for the management driver. Please consult with your storage and security administrator regarding the preferred authentication method and how passwords or SSH keys should be stored in a secure manner.


When creating a new user on the Storwize or SVC system, make sure the user belongs to the Administrator group or to another group that has an Administrator role.

If using password authentication, assign a password to the user on the Storwize or SVC system. The driver configuration flags for the user and password are san_login and san_password, respectively.

If you are using the SSH key pair authentication, create SSH private and public keys using the instructions below or by any other method. Associate the public key with the user by uploading the public key: select the choose file option in the Storwize family or SVC management GUI under SSH public key. Alternatively, you may associate the SSH public key using the command-line interface; details can be found in the Storwize and SVC documentation. The private key should be provided to the driver using the san_private_key configuration flag.

Create a SSH key pair with OpenSSH

You can create an SSH key pair using OpenSSH, by running:

$ ssh-keygen -t rsa

The command prompts for a file to save the key pair. For example, if you select key as the filename, two files are created: key and The key file holds the private SSH key and holds the public SSH key.

The command also prompts for a pass phrase, which should be empty.

The private key file should be provided to the driver using the san_private_key configuration flag. The public key should be uploaded to the Storwize family or SVC system using the storage management GUI or command-line interface.


Ensure that Cinder has read permissions on the private key file.

Configure the Storwize family and SVC driver

Enable the Storwize family and SVC driver

Set the volume driver to the Storwize family and SVC driver by setting the volume_driver option in the cinder.conf file as follows:


volume_driver =
san_ip =
san_login = superuser
san_password = passw0rd
storwize_svc_volpool_name = cinder_pool1
volume_backend_name = svc1234


volume_driver =
san_ip =
san_login = superuser
san_password = passw0rd
storwize_svc_volpool_name = cinder_pool1
volume_backend_name = svc1234

Replication configuration

Add the following to the back-end specification to specify another storage to replicate to:

replication_device = backend_id:rep_svc,

The backend_id is a unique name of the remote storage, the san_ip, san_login, and san_password is authentication information for the remote storage. The pool_name is the pool name for the replication target volume.


Only one replication_device can be configured for one back end storage since only one replication target is supported now.

Storwize family and SVC driver options in cinder.conf

The following options specify default values for all volumes. Some can be over-ridden using volume types, which are described below.

Description of IBM Storwise driver configuration options
Configuration option = Default value Description
san_ip = (String) IP address of SAN controller
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 number) SSH port to use with SAN
storwize_san_secondary_ip = None (String) Specifies secondary management IP or hostname to be used if san_ip is invalid or becomes inaccessible.
storwize_svc_allow_tenant_qos = False (Boolean) Allow tenants to specify QOS on create
storwize_svc_flashcopy_rate = 50 (Integer) Specifies the Storwize FlashCopy copy rate to be used when creating a full volume copy. The default is rate is 50, and the valid rates are 1-100.
storwize_svc_flashcopy_timeout = 120 (Integer) Maximum number of seconds to wait for FlashCopy to be prepared.
storwize_svc_iscsi_chap_enabled = True (Boolean) Configure CHAP authentication for iSCSI connections (Default: Enabled)
storwize_svc_multihostmap_enabled = True (Boolean) DEPRECATED: This option no longer has any affect. It is deprecated and will be removed in the next release.
storwize_svc_multipath_enabled = False (Boolean) Connect with multipath (FC only; iSCSI multipath is controlled by Nova)
storwize_svc_stretched_cluster_partner = None (String) If operating in stretched cluster mode, specify the name of the pool in which mirrored copies are stored.Example: “pool2”
storwize_svc_vol_autoexpand = True (Boolean) Storage system autoexpand parameter for volumes (True/False)
storwize_svc_vol_compression = False (Boolean) Storage system compression option for volumes
storwize_svc_vol_easytier = True (Boolean) Enable Easy Tier for volumes
storwize_svc_vol_grainsize = 256 (Integer) Storage system grain size parameter for volumes (32/64/128/256)
storwize_svc_vol_iogrp = 0 (Integer) The I/O group in which to allocate volumes
storwize_svc_vol_nofmtdisk = False (Boolean) Specifies that the volume not be formatted during creation.
storwize_svc_vol_rsize = 2 (Integer) Storage system space-efficiency parameter for volumes (percentage)
storwize_svc_vol_warning = 0 (Integer) Storage system threshold for volume capacity warnings (percentage)
storwize_svc_volpool_name = volpool (List) Comma separated list of storage system storage pools for volumes.

Note the following:

  • The authentication requires either a password (san_password) or SSH private key (san_private_key). One must be specified. If both are specified, the driver uses only the SSH private key.
  • The driver creates thin-provisioned volumes by default. The storwize_svc_vol_rsize flag defines the initial physical allocation percentage for thin-provisioned volumes, or if set to -1, the driver creates full allocated volumes. More details about the available options are available in the Storwize family and SVC documentation.

Placement with volume types

The IBM Storwize/SVC driver exposes capabilities that can be added to the extra specs of volume types, and used by the filter scheduler to determine placement of new volumes. Make sure to prefix these keys with capabilities: to indicate that the scheduler should use them. The following extra specs are supported:

  • capabilities:volume_back-end_name - Specify a specific back-end where the volume should be created. The back-end name is a concatenation of the name of the IBM Storwize/SVC storage system as shown in lssystem, an underscore, and the name of the pool (mdisk group). For example:

  • capabilities:compression_support - Specify a back-end according to compression support. A value of True should be used to request a back-end that supports compression, and a value of False will request a back-end that does not support compression. If you do not have constraints on compression support, do not set this key. Note that specifying True does not enable compression; it only requests that the volume be placed on a back-end that supports compression. Example syntax:

    capabilities:compression_support='<is> True'
  • capabilities:easytier_support - Similar semantics as the compression_support key, but for specifying according to support of the Easy Tier feature. Example syntax:

    capabilities:easytier_support='<is> True'
  • capabilities:storage_protocol - Specifies the connection protocol used to attach volumes of this type to instances. Legal values are iSCSI and FC. This extra specs value is used for both placement and setting the protocol used for this volume. In the example syntax, note <in> is used as opposed to <is> which is used in the previous examples.

    capabilities:storage_protocol='<in> FC'

Configure per-volume creation options

Volume types can also be used to pass options to the IBM Storwize/SVC driver, which over-ride the default values set in the configuration file. Contrary to the previous examples where the capabilities scope was used to pass parameters to the Cinder scheduler, options can be passed to the IBM Storwize/SVC driver with the drivers scope.

The following extra specs keys are supported by the IBM Storwize/SVC driver:

  • rsize
  • warning
  • autoexpand
  • grainsize
  • compression
  • easytier
  • multipath
  • iogrp

These keys have the same semantics as their counterparts in the configuration file. They are set similarly; for example, rsize=2 or compression=False.

Example: Volume types

In the following example, we create a volume type to specify a controller that supports iSCSI and compression, to use iSCSI when attaching the volume, and to enable compression:

$ openstack volume type create compressed
$ openstack volume type set --property capabilities:storage_protocol='<in> iSCSI' capabilities:compression_support='<is> True' drivers:compression=True

We can then create a 50GB volume using this type:

$ openstack volume create "compressed volume" --type compressed --size 50

In the following example, create a volume type that enables synchronous replication (metro mirror):

$ openstack volume type create ReplicationType
$ openstack volume type set --property replication_type="<in> metro" \
  --property replication_enabled='<is> True' --property volume_backend_name=svc234 ReplicationType

Volume types can be used, for example, to provide users with different

  • performance levels (such as, allocating entirely on an HDD tier, using Easy Tier for an HDD-SDD mix, or allocating entirely on an SSD tier)
  • resiliency levels (such as, allocating volumes in pools with different RAID levels)
  • features (such as, enabling/disabling Real-time Compression, replication volume creation)


The Storwize driver provides QOS support for storage volumes by controlling the I/O amount. QOS is enabled by editing the etc/cinder/cinder.conf file and setting the storwize_svc_allow_tenant_qos to True.

There are three ways to set the Storwize IOThrotting parameter for storage volumes:

  • Add the qos:IOThrottling key into a QOS specification and associate it with a volume type.
  • Add the qos:IOThrottling key into an extra specification with a volume type.
  • Add the qos:IOThrottling key to the storage volume metadata.


If you are changing a volume type with QOS to a new volume type without QOS, the QOS configuration settings will be removed.

Operational notes for the Storwize family and SVC driver

Migrate volumes

In the context of OpenStack Block Storage’s volume migration feature, the IBM Storwize/SVC driver enables the storage’s virtualization technology. When migrating a volume from one pool to another, the volume will appear in the destination pool almost immediately, while the storage moves the data in the background.


To enable this feature, both pools involved in a given volume migration must have the same values for extent_size. If the pools have different values for extent_size, the data will still be moved directly between the pools (not host-side copy), but the operation will be synchronous.

Extend volumes

The IBM Storwize/SVC driver allows for extending a volume’s size, but only for volumes without snapshots.

Snapshots and clones

Snapshots are implemented using FlashCopy with no background copy (space-efficient). Volume clones (volumes created from existing volumes) are implemented with FlashCopy, but with background copy enabled. This means that volume clones are independent, full copies. While this background copy is taking place, attempting to delete or extend the source volume will result in that operation waiting for the copy to complete.

Volume retype

The IBM Storwize/SVC driver enables you to modify volume types. When you modify volume types, you can also change these extra specs properties:

  • rsize
  • warning
  • autoexpand
  • grainsize
  • compression
  • easytier
  • iogrp
  • nofmtdisk


When you change the rsize, grainsize or compression properties, volume copies are asynchronously synchronized on the array.


To change the iogrp property, IBM Storwize/SVC firmware version 6.4.0 or later is required.

Replication operation

A volume is only replicated if the volume is created with a volume-type that has the extra spec replication_enabled set to <is> True. Two types of replication are supported now, async (global mirror) and sync (metro mirror). It can be specified by a volume-type that has the extra spec replication_type set to <in> global or replication_type set to <in> metro. If no replication_type is specified, global mirror will be created for replication.


It is better to establish the partnership relationship between the replication source storage and the replication target storage manually on the storage back end before replication volume creation.

The failover-host command is designed for the case where the primary storage is down.

$ cinder failover-host cinder@svciscsi --backend_id target_svc_id

If a failover command has been executed and the primary storage has been restored, it is possible to do a failback by simply specifying default as the backend_id:

$ cinder failover-host cinder@svciscsi --backend_id default


Before you perform a failback operation, synchronize the data from the replication target volume to the primary one on the storage back end manually, and do the failback only after the synchronization is done since the synchronization may take a long time. If the synchronization is not done manually, Storwize Block Storage service driver will perform the synchronization and do the failback after the synchronization is finished.

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