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Volume Guides

Guides for managing volumes and backups

1: Volume Attachment Limits
2: Volume Backup & Restore
3: Volume migration
4: Volume Retype
5: Windows volume offline after restart

1 - Volume Attachment Limits

Guide to increasing the volume attachment limit in Openstack

Overview

If you need to attach more than the default limitation of volume attachments, then this is possible by using a custom image and changing the properties of the image to use a non-default scsi driver.

Please note that any servers created before the image properties are set need to be re-created in order to use the updated driver.

The following properties need to be set in order to achieve this.

hw_disk_bus=scsi
hw_scsi_model=virtio-scsi

Volume attachment limits

Driver	Max volumes per server
Default	26
virtio-scsi	128

Openstack CLI examples

Creating a new image (note that additional options are also needed when creating images, please refer to the Openstack documentation for more information)

openstack image create --property hw_disk_bus=scsi --property hw_scsi_model=virtio-scsi ${IMAGE_ID}

Updating an existing private image

openstack image set --property hw_disk_bus=scsi --property hw_scsi_model=virtio-scsi ${IMAGE_ID}

2 - Volume Backup & Restore

Guide to backup & restore a Volume

Overview

Volume backups in Elastx OpenStack uses Swift as the storage backend. This means that your backups will automatically be placed in all availability zones. This guide will help you get started with how to create volume backups and how to restore them using OpenStack’s Horizon and CLI.

Backup and restrore from Horizon

Backup from Horizon

Navigate to “Project” → “Volumes” pick the volume you want to backup and choose Create Backup

Open-create-backup

In the pop-up window, add a name and a description of your liking and press Create Volume Backup.

Create-backup

Navigate to “Project” → “Volumes” → “Backups” to see the backup status.

Status-create-backup

Restore from horizon

Restoring from backups can be done in two ways, one way is to create a new volume manually from the “Project” → “Volumes”, or to have the volume automatically created when restoring from the “Project” → “Volumes” → “Backups”.

Beware: If option two is chosen, the Availability Zone and Size gets chosen automatically. This means that the volume might end up in a different Availability Zone than intended.

Option #1 - Create volume and restore from backup

Navigate to “Project” → “Volumes” and press Create Volume.

Status-create-volume

Choose a name, description and size of your liking for the new volume.

Beware: Volume Size has to be at minimum the size of the backup. The Volume also has to be in the same Availability Zone as the instance it will be attached too.

Status-create-volume

Navigate to “Project” → “Volumes” → “Backups” and press Restore Backup.

Status-restore-volume

Select your newly created volume and press Restore Backup to Volume.

Status-restore-volume

Option #2 - Restore backup without selecting a volume

Beware: See the note about availability zones and sizes above.

Navigate to “Project” → “Volumes” → “Backups” and press Restore Backup.

Status-restore-volume

Select Create a New Volume and press Restore Backup to Volume.

Status-restore-volume

The restored backup will be available in “Project” → “Volumes”.

Status-restore-volume

Attach & Detach volumes from horizon

Navigate to “Project” → “Volumes” and press the ⬇ arrow next to Edit Volume on the volume you want to attach and then press Manage Attachments

Status-attach-volume

In the pop-up window choose an instance you want to attach the restored volume to.

Status-attach-volume

Check volumes again in “Project” → “Volumes” to see if the volume is attached to the instance.

Status-attach-volume

To detach the volume, Navigate to “Project” → “Volumes” and press the ⬇ arrow next to Edit Volume on the volume you want to detach and then press Manage Attachments. In the pop-up window choose the instance you want to detach the volume from.

Status-attach-volume

Backup and restore using openstack-cli

Backup using cli

List all volumes:

$ openstack volume list

+--------------------------------------+----------+--------+------+-------------------------------------+
| ID                                   | Name     | Status | Size | Attached to                         |
+--------------------------------------+----------+--------+------+-------------------------------------+
| ce29137e-d7d7-45a6-ae63-bb6605af5335 | myvolume | in-use |  100 | Attached to myinstance on /dev/vdb  |
+--------------------------------------+--------------------------------------+-----------+------+------+

Create backup of your selected volume:

Beware: If the volume is attached to an instance you’ll need to detach it first or use --force when creating the backup.

$ openstack volume backup create ce29137e-d7d7-45a6-ae63-bb6605af5335 --name mybackup --description "my backup" --force

+-----------+--------------------------------------+
| Field     | Value                                |
+-----------+--------------------------------------+
| id        | b014e2c4-42a9-44d5-af9b-60f3cf7ecfc9 |
| name      | mybackup                             |
| volume_id | ce29137e-d7d7-45a6-ae63-bb6605af5335 |
+-----------+--------------------------------------+

When the backup is finished, the status will change from creating to available.

$ openstack volume backup list --volume ce29137e-d7d7-45a6-ae63-bb6605af5335

+--------------------------------------+----------+-------------+-----------+------+-------------+----------------------------+
| ID                                   | Name     | Description | Status    | Size | Incremental | Created At                 |
+--------------------------------------+----------+-------------+-----------+------+-------------+----------------------------+
| b014e2c4-42a9-44d5-af9b-60f3cf7ecfc9 | mybackup | my backup   | available |  100 | False       | 2026-01-23T11:18:01.000000 |
+--------------------------------------+----------+-------------+-----------+------+-------------+----------------------------+

Restore using cli

Restoring from backups can be done in two ways, one way is to create a new volume manually or to have the volume automatically created when restoring. Size must be at minimum the size of the backup.

Beware: If second option is chosen, the Availability Zone and Size gets chosen automatically. This means that the volume might end up in a different Availability Zone than intended. Volume size must be at minimum the size of the backup.

List available backups:

$ openstack volume backup list

+--------------------------------------+----------+-------------+-----------+------+-------------+----------------------------+
| ID                                   | Name     | Description | Status    | Size | Incremental | Created At                 |
+--------------------------------------+----------+-------------+-----------+------+-------------+----------------------------+
| b014e2c4-42a9-44d5-af9b-60f3cf7ecfc9 | mybackup | my backup   | available |  100 | False       | 2026-01-23T11:18:01.000000 |
+--------------------------------------+----------+-------------+-----------+------+-------------+----------------------------+

Create a new volume to restore from the backup:

$ openstack volume create my_volume_restore --availability-zone sto2 --type v2-4k --size 100 --description restored_from_backup

+--------------------------------+--------------------------------------+
| Field                          | Value                                |
+--------------------------------+--------------------------------------+
| attachments                    | []                                   |
| availability_zone              | sto2                                 |
| backup_id                      | None                                 |
| created_at                     | 2026-01-27T08:37:22.083078           |
| description                    | restored_from_backup                 |
| encrypted                      | False                                |
| group_id                       | None                                 |
| id                             | 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 |
| multiattach                    | False                                |
| name                           | my_volume_restore                    |
| size                           | 100                                  |
| status                         | creating                             |
| type                           | v2-4k                                |
| updated_at                     | None                                 |
| volume_type_id                 | 565d82f0-238d-4f90-9aa4-172f0594bd58 |
+--------------------------------+--------------------------------------+

Restore your selected backup to the newly created volume:

Beware: You’ll need to use –force to be able to restore backup to your newly created volume. Make sure to select the correct volume as this will overwrite any existing data.

$ openstack volume backup restore mybackup my_volume_restore --force

+-------------+--------------------------------------+
| Field       | Value                                |
+-------------+--------------------------------------+
| id          | b014e2c4-42a9-44d5-af9b-60f3cf7ecfc9 |
| volume_id   | 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 |
| volume_name | my_volume_restore                    |
+-------------+--------------------------------------+

After the backup is fully restored your new volume will show as: available.

$ openstack volume list

+--------------------------------------+-------------------+-----------+------+---------------------------------+
| ID                                   | Name              | Status    | Size | Attached to                     |
+--------------------------------------+-------------------+-----------+------+---------------------------------+
| 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 | my_volume_restore | available |  100 |                                 |
| ce29137e-d7d7-45a6-ae63-bb6605af5335 | myvolume          | available |  100 |                                 |
+--------------------------------------+--------------------------------------+-----------+------+--------------+

Attach & Detach volumes from cli

Attach

List all available volumes:

$ openstack volume list --status available

+--------------------------------------+----------+--------+------+-------------------------------------+
| ID                                   | Name     | Status | Size | Attached to                         |
+--------------------------------------+----------+--------+------+-------------------------------------+
| ce29137e-d7d7-45a6-ae63-bb6605af5335 | myvolume | in-use |  100 | Attached to myinstance on /dev/vdb  |
+--------------------------------------+--------------------------------------+-----------+------+------+

List all instances:

$ openstack server list

+--------------------------------------+------------+---------+--------------------------------+----------------------------+---------------+
| ID                                   | Name       | Status  | Networks                       | Image                      | Flavor        |
+--------------------------------------+------------+---------+--------------------------------+----------------------------+---------------+
| 3e55aef3-09a6-49e8-87ac-779354a1b7cd | myinstance | ACTIVE  | testnet=192.168.30.19          | ubuntu-24.04-server-latest | v2-c4-m8-d120 |
+--------------------------------------+------------+--------+---------------------------------+----------------------------+---------------+

Attach your restored volume to an instance: openstack server add volume <Instance ID/Name> <Volume ID/Name>

$ openstack server add volume myinstance my_volume_restore

+-----------------------+--------------------------------------+
| Field                 | Value                                |
+-----------------------+--------------------------------------+
| ID                    | 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 |
| Server ID             | 3e55aef3-09a6-49e8-87ac-779354a1b7cd |
| Volume ID             | 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 |
| Device                | /dev/vdb                             |
| Tag                   | None                                 |
| Delete On Termination | False                                |
+-----------------------+--------------------------------------+

Confirm the attachment:

$ openstack volume list

+--------------------------------------+-------------------+-----------+------+-------------------------------------+
| ID                                   | Name              | Status    | Size | Attached to                         |
+--------------------------------------+-------------------+-----------+------+-------------------------------------+
| 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 | my_volume_restore | in-use    |  100 | Attached to myinstance on /dev/vdb  |
| ce29137e-d7d7-45a6-ae63-bb6605af5335 | myvolume          | available |  100 |                                     |
+--------------------------------------+-------------------+-----------+------+-------------------------------------+

Detach

Detach a volume from an instance: openstack server remove volume <Instance ID/Name> <Volume ID/Name>.

$ openstack server remove volume myinstance my_volume_restore

Confirm the detachment:

$ openstack volume list

+--------------------------------------+-------------------+-----------+------+---------------------------------+
| ID                                   | Name              | Status    | Size | Attached to                     |
+--------------------------------------+-------------------+-----------+------+---------------------------------+
| 6b5b8d28-d6c1-4da0-8659-d607670f5ed9 | my_volume_restore | available |  100 |                                 |
| ce29137e-d7d7-45a6-ae63-bb6605af5335 | myvolume          | available |  100 |                                 |
+--------------------------------------+--------------------------------------+---------------------------------+

3 - Volume migration

Migrate volume data between Availability Zones

Overview

To migrate volume data between Availability Zones (sto1|sto2|sto3) you can use Openstacks backup functionality. This backup process uses our Swift object storage, which is available across all Availability Zones.

Shutdown the instance whose volume will change Availability Zone. Let’s say it’s in sto1 now.
Take a backup of the volume (this may take some time, depending on the size of the volume).
Create a new volume in Availability Zone sto2 and select the backup as the source.
Create a new instance in Availability Zone sto2 and attach the newly created volume.

To get a more in-depth look at how to perform backup and restore of a volume, follow our Volume Backup & Restore guide.

4 - Volume Retype

Guide to change volume type

Overview

This guide will help you getting started with changing volume type in OpenStack.

Note

For v2 volumes as well as the deprecated ’enc’ volume types you will need to detach the volume from your server before retyping. Either shut down your server or unmount the volume in your operating system before detaching the volume in Openstack.

You cannot change a volume type from v1 to v2 if it has an existing snapshot.

Volume retype from Horizon

In this example, we will use a detached volume with the type 16k-IOPS-enc.

Navigate to “Project” → “Volumes” choose the volume you want to retype and press the ⬇ arrow next to Edit Volume and select Change Volume Type.

Open-create-backup

Choose Type

In the pop-up window, choose a new type and set Migration Policy to On Demand.

Create-backup

Check status

The volume status will change to retyping, this can take a while depending on the volume size. After everything is done, the volume will have the status available.

Status-create-backup

Volume retype using OpenStack CLI

List all available volumes: openstack volume list --long.

openstack volume list --long
+--------------------------------------+------------------+-----------+------+--------------+----------+--------------------------------------+--------------------------------------+
| ID                                   | Name             | Status    | Size | Type         | Bootable | Attached to                          | Properties                           |
+--------------------------------------+------------------+-----------+------+--------------+----------+--------------------------------------+--------------------------------------+
| ad2ca224-78e0-4930-941e-596bbea05b95 | encrypted-volume | available |    1 | 16k-IOPS-enc | false    |                                      |                                      |
| db329723-1a3e-4fb9-be07-da6e0a5ff0b1 |                  | in-use    |   20 | 4k-IOPS      | true     | Attached to docker-test on /dev/vda  | attached_mode='rw', readonly='False' |
+--------------------------------------+------------------+-----------+------+--------------+----------+--------------------------------------+--------------------------------------+

Retype volume with: openstack volume set --type <volume-type> --retype-policy on-demand <Volume ID or Name>.

openstack volume set --type 16k-IOPS --retype-policy on-demand ad2ca224-78e0-4930-941e-596bbea05b95

openstack volume list --long
+--------------------------------------+------------------+----------+------+--------------+----------+--------------------------------------+--------------------------------------+
| ID                                   | Name             | Status   | Size | Type         | Bootable | Attached to                          | Properties                           |
+--------------------------------------+------------------+----------+------+--------------+----------+--------------------------------------+--------------------------------------+
| ad2ca224-78e0-4930-941e-596bbea05b95 | encrypted-volume | retyping |    1 | 16k-IOPS-enc | false    |                                      |                                      |
| db329723-1a3e-4fb9-be07-da6e0a5ff0b1 |                  | in-use   |   20 | 4k-IOPS      | true     | Attached to docker-test on /dev/vda  | attached_mode='rw', readonly='False' |
+--------------------------------------+------------------+----------+------+--------------+----------+--------------------------------------+--------------------------------------+

When retyping is done, status will be shown as: available.

openstack volume list --long
+--------------------------------------+------------------+-----------+------+----------+----------+--------------------------------------+--------------------------------------+
| ID                                   | Name             | Status    | Size | Type     | Bootable | Attached to                          | Properties                           |
+--------------------------------------+------------------+-----------+------+----------+----------+--------------------------------------+--------------------------------------+
| ad2ca224-78e0-4930-941e-596bbea05b95 | encrypted-volume | available |    1 | 16k-IOPS | false    |                                      |                                      |
| db329723-1a3e-4fb9-be07-da6e0a5ff0b1 |                  | in-use    |   20 | 4k-IOPS  | true     | Attached to docker-test on /dev/vda  | attached_mode='rw', readonly='False' |
+--------------------------------------+------------------+-----------+------+----------+----------+--------------------------------------+--------------------------------------+

5 - Windows volume offline after restart

Guide to preventing volumes from going offline in Windows servers

Issue description

In certain circumstances, extra disks can be marked as offline after a hard reboot is performed and have to be manually brought online again.

By default Windows machines will have the SAN policy set to be “Offline Shared”, thus in most virtualization platforms this issue will occur when a disk is completely shut down and started again.

The reason behind this is that the disk may be assigned to a different virtual PCI device in the underlying host which causes the OS to block the volume from going online automatically when using the default policy.

Change SAN policy

The easiest way to change the SAN policy is using diskpart in a command shell or powershell prompt.

Enter diskpart
```
diskpart
```
To display the current SAN policy, simply run the following command
```
san
```
Change SAN policy
```
san policy=OnlineAll
```

Restore offline volume state

When attempting to initialize a volume you may be seeing the following error

The disk is offline because of policy set by an administrator

Start by listing disk information to find out which disk is offline.
```
list disk
```
Select the offline disk.
```
select disk 1
```
Clear the read-only attribute for the selected disk.
```
attributes disk clear readonly
```
To check that the read-only attribute has been cleared, run the following command.
```
attributes disk
```
Bring the selected disk online again.
```
online disk
```

Volume Guides

1 - Volume Attachment Limits

Overview

Volume attachment limits

Openstack CLI examples

2 - Volume Backup & Restore

Overview

Backup and restrore from Horizon

Backup from Horizon

Restore from horizon

Option #1 - Create volume and restore from backup

Option #2 - Restore backup without selecting a volume

Attach & Detach volumes from horizon

Backup and restore using openstack-cli

Backup using cli

Restore using cli

Attach & Detach volumes from cli

Attach

Detach

Further reading

3 - Volume migration

Overview

4 - Volume Retype

Overview

Volume retype from Horizon

Choose Type

Check status

Volume retype using OpenStack CLI

Further reading

5 - Windows volume offline after restart

Issue description

Change SAN policy

Restore offline volume state