OpenStack Cinder File System Configuration

This guide describes an optional file system that can be used by Cinder to convert qcow2 images to raw format.


By default, qcow2 image conversion is done using the docker_lv file system. To avoid filling up the docker_lv file system, you can create a new file system that is dedicated to image conversion using the steps in this guide.

Add new file system

Use the host-fs-add CLI command to add a file system dedicated to qcow2 image conversion.

The syntax is:

system host-fs-add <hostname or id> <fs name=size>


  • hostname or id is the location where the file system will be added.

  • fs name is the file system name.

  • size is an integer indicating the file system size in Gigabytes.

When the command completes, a new partition named /opt/conversion is created and mounted.

You must add the file system on both controller nodes. You can do this from controller-0 using the following example commands:

system host-fs-add controller-0 image-conversion=20
system host-fs-add controller-1 image-conversion=20


  1. The requested size of the image-conversion file system should be big enough to accommodate any image that is uploaded to glance. If the requested size is too large, the command will fail.

  2. The recommended size for the file system is at least 2 times as large as the largest converted image from qcow2 to raw.

  3. The conversion file system can be added before or after stx-openstack is applied.

  4. The conversion file system must be added on both controllers. If not, stx-openstack will not use the new file system.

  5. If the conversion file system is added after stx-openstack is applied, changes to stx-openstack will only take effect once the application is re-applied.

The image-conversion file system can be added only on controller nodes.

Alarms for image-conversion will be raised for the following scenarios:

  • If the conversion file system is not added on both controllers.

  • If the size of the file system is not the same on both controllers.

Resize the file system

Change the size of the image-conversion file system at runtime using the following CLI command:

system host-fs-modify <hostname or id> <fs name=size>

For example:

system host-fs-modify controller-0 image-conversion=30

Remove the file system

Use the host-fs-delete CLI command to remove an image-conversion file system dedicated to qcow2 image conversion.

The syntax is:

system host-fs-delete <hostname or id> <fs name>

When image-conversion is removed, the /opt/conversion partition is also removed.


You cannot delete an image-conversion file system when stx-openstack is in the applying, applied, or removing state.

You cannot add or remove any other file systems using these commands.