Changing a volume’s type

You may occasionally need to change the type of a volume. This may be due to a volume type being phased out on Cleura Cloud’s part, necessitating data migration. Or you might want to enable or disable volume-level encryption.

Changing the type of a volume (“retyping”) is an offline operation that requires detaching the volume from its server, and setting its new type. The process of volume retyping incurs a short downtime. Depending on the kind of application the server hosts, when you need to retype volumes, you should plan ahead well in advance.

Prerequisites

In order to retype volumes, you must use the OpenStack CLI, so make sure you have it enabled.

Checking the volume’s state

Assume you have a volume named testvol that is currently attached to a server named testsrv:

$ openstack volume list --long
+--------------+---------+--------+------+-------------+----------+--------------+------------+
| ID           | Name    | Status | Size | Type        | Bootable | Attached to  | Properties |
+--------------+---------+--------+------+-------------+----------+--------------+------------+
| 0e6f15f8-    | testvol | in-use |   75 | cbs-premium | false    | Attached to  |            |
| 8105-4043-   |         |        |      |             |          | testsrv on   |            |
| beb1-        |         |        |      |             |          | /dev/vdb     |            |
| 43f2364460f2 |         |        |      |             |          |              |            |
+--------------+---------+--------+------+-------------+----------+--------------+------------+

In this example, this volume status is in-use, meaning it is currently attached to a server, and the volume type is cbs-premium.

Detaching the volume

You cannot retype a volume while it is attached to a server. You must thus detach it first. It is safest to do this while the server is shut down:

$ openstack server stop testsrv

$ openstack server list -c Name -c Status
+---------+---------+
| Name    | Status  |
+---------+---------+
| testsrv | SHUTOFF |
+---------+---------+

Once your server is in the SHUTOFF state, you can safely proceed to detaching the volume. This will change the volume status from in-use to available.

$ openstack server remove volume testsrv testvol

$ openstack volume list
+--------------------------------------+---------+-----------+------+-------------+
| ID                                   | Name    | Status    | Size | Attached to |
+--------------------------------------+---------+-----------+------+-------------+
| 0e6f15f8-8105-4043-beb1-43f2364460f2 | testvol | available |   75 |             |
+--------------------------------------+---------+-----------+------+-------------+

Retyping the volume

With the volume safely detached, you can now change its volume type. If you were to change the volume type from cbs-premium to cbs-standard, you would proceed as follows:

$ openstack volume set --type cbs-standard --migration-policy on-demand testvol

$ openstack volume list --long
+-------------+---------+-----------+------+-------------+----------+-------------+------------+
| ID          | Name    | Status    | Size | Type        | Bootable | Attached to | Properties |
+-------------+---------+-----------+------+-------------+----------+-------------+------------+
| 0e6f15f8-   | testvol | available |   75 | cbs-        | false    |             |            |
| 8105-4043-  |         |           |      | standard    |          |             |            |
| beb1-       |         |           |      |             |          |             |            |
| 43f2364460f |         |           |      |             |          |             |            |
| 2           |         |           |      |             |          |             |            |
+-------------+---------+-----------+------+-------------+----------+-------------+------------+

Re-attaching the volume

Once retyping is complete and the volume is in the available status, you can re-attach it to the server:

$ openstack server add volume testsrv testvol

+-----------------------+--------------------------------------+
| Field                 | Value                                |
+-----------------------+--------------------------------------+
| ID                    | 0e6f15f8-8105-4043-beb1-43f2364460f2 |
| Server ID             | 42049bba-3a48-4bc3-9940-bcaca120ec74 |
| Volume ID             | 0e6f15f8-8105-4043-beb1-43f2364460f2 |
| Device                | /dev/vdb                             |
| Tag                   | None                                 |
| Delete On Termination | False                                |
+-----------------------+--------------------------------------+

Finally, start the server:

$ openstack server start testsrv

$ openstack server list -c Name -c Status
+---------+--------+
| Name    | Status |
+---------+--------+
| testsrv | ACTIVE |
+---------+--------+