LVM support in cinder charm: migration to cinder-lvm

As of the 21.10 release of OpenStack Charms, support for local (LVM) Cinder storage in the cinder charm is deprecated. This functionality has been de-coupled and is now managed by the cinder-lvm subordinate charm. This page shows how to migrate from the cinder charm to the cinder-lvm charm.

Warning

The migration will necessitate a short cloud maintenance window, enough time to deploy the subordinate charm onto the existing machine(s). Cloud operators will be unable to create new Cinder volumes during this window.

The LVM feature in the cinder charm is potentially in use if the block-device option is set to a value other than ‘None’. Check this with the following command:

juju config cinder block-device

Begin by disabling the LVM feature in the cinder charm:

juju config cinder block-device=None

Migrating LVM functionality amounts to setting the cinder-lvm charm configuration options to the same values as those used for the identically named options in the cinder charm:

• block-device

• ephemeral-unmount

• remove-missing

• remove-missing-force

• overwrite

• volume-group

Secondly, the volume-backend-name option specific to the cinder-lvm charm needs to be set to ‘cinder_lvm’, the LVM backend driver.

All of this configuration can be stated most easily with a configuration file, say cinder-lvm.yaml:

cinder-lvm:
  block-device: sdb
  ephemeral-unmount: <null>
  remove-missing: false
  remove-missing-force: false
  overwrite: false
  volume-group: cinder-volumes
  volume-backend-name: cinder_lvm

Now deploy cinder-lvm while referencing the configuration file and then add a relation to the cinder application:

juju deploy --config cinder-lvm.yaml cinder-lvm
juju add-relation cinder-lvm:storage-backend cinder:storage-backend

Verify that Cinder volumes can be created as usual and that existing VMs utilising Cinder volumes have not been adversely affected.