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Taikun OCP Guide

Table of Contents

Manage volumes

Depending on the setup of your cloud provider, they may give you an
endpoint to use to manage volumes. You can use the
openstack CLI to manage volumes.

For the purposes of the compute service, attaching, detaching and
creating a server from a volume </user/launch-instance-from-volume>
are of primary interest.

Refer to the CLI documentation
<cli/command-objects/volume.html>
for more information.

Volume multi-attach

Nova added
support for multiattach volumes
in the 17.0.0 Queens release.

This document covers the nova-specific aspects of this feature. Refer
to the block storage admin guide
<admin/blockstorage-volume-multiattach.html>
for more
details about creating multiattach-capable volumes.

Boot from volume <Boot From Volume> and
attaching a volume to a server that is not SHELVED_OFFLOADED is
supported. Ultimately the ability to perform these actions depends on
the compute host and hypervisor driver that is being used.

There is also a recorded overview and
demo
for volume multi-attach.

Requirements

  • The minimum required compute API microversion for attaching a
    multiattach-capable volume to more than one server is 2.60
    <api-microversion-queens>
    .
  • Cinder 12.0.0 (Queens) or newer is required.
  • The nova-compute service must be running at least
    Queens release level code (17.0.0) and the hypervisor driver must
    support attaching block storage devices to more than one guest. Refer to
    /user/support-matrix
    for details on which compute drivers support volume multiattach.
  • When using the libvirt compute driver, the following native package
    versions determine multiattach support:

    • libvirt must be greater than or equal to 3.10, or
    • qemu must be less than 2.10
  • Swapping an in-use multiattach volume is not supported
    (this is actually controlled via the block storage volume retype
    API).

Known issues

  • Creating multiple servers in a single request with a
    multiattach-capable volume as the root disk is not yet supported: https://bugs.launchpad.net/nova/+bug/1747985
  • Subsequent attachments to the same volume are all attached in
    read/write mode by default in the block storage service. A
    future change either in nova or cinder may address this so that
    subsequent attachments are made in read-only mode, or such that
    the mode can be specified by the user when attaching the volume to the
    server.

Testing

Continuous integration testing of the volume multiattach feature is
done via the tempest-full and tempest-slow
jobs, which, along with the tests themselves, are defined in the tempest
repository
.

Managing volume attachments

During the lifecycle of an instance admins may need to check various
aspects of how a given volume is mapped both to an instance and the
underlying compute hosting the instance. This could even include
refreshing different elements of the attachment to ensure the latest
configuration changes within the environment have been applied.

Checking an existing
attachment

Existing volume attachments can be checked using the following OpenStack Client commands <cli/command-objects>:

List all volume attachments for a given instance:

$ openstack server volume list 216f9481-4c9d-4530-b865-51cedfa4b8e7
+--------------------------------------+----------+--------------------------------------+--------------------------------------+
| ID                                   | Device   | Server ID                            | Volume ID                            |
+--------------------------------------+----------+--------------------------------------+--------------------------------------+
| 8b9b3491-f083-4485-8374-258372f3db35 | /dev/vdb | 216f9481-4c9d-4530-b865-51cedfa4b8e7 | 8b9b3491-f083-4485-8374-258372f3db35 |
+--------------------------------------+----------+--------------------------------------+--------------------------------------+

List all volume attachments for a given instance with the Cinder
volume attachment and Block Device Mapping UUIDs also listed with
microversion >=2.89:

$ openstack --os-compute-api-version 2.89 server volume list 216f9481-4c9d-4530-b865-51cedfa4b8e7
+----------+--------------------------------------+--------------------------------------+------+------------------------+--------------------------------------+--------------------------------------+
| Device   | Server ID                            | Volume ID                            | Tag  | Delete On Termination? | Attachment ID                        | BlockDeviceMapping UUID              |
+----------+--------------------------------------+--------------------------------------+------+------------------------+--------------------------------------+--------------------------------------+
| /dev/vdb | 216f9481-4c9d-4530-b865-51cedfa4b8e7 | 8b9b3491-f083-4485-8374-258372f3db35 | None | False                  | d338fb38-cfd5-461f-8753-145dcbdb6c78 | 4e957e6d-52f2-44da-8cf8-3f1ab755e26d |
+----------+--------------------------------------+--------------------------------------+------+------------------------+--------------------------------------+--------------------------------------+

List all Cinder volume attachments for a given volume from
microversion >= 3.27:

$ openstack --os-volume-api-version 3.27 volume attachment list --volume-id 8b9b3491-f083-4485-8374-258372f3db35
+--------------------------------------+--------------------------------------+--------------------------------------+----------+
| ID                                   | Volume ID                            | Server ID                            | Status   |
+--------------------------------------+--------------------------------------+--------------------------------------+----------+
| d338fb38-cfd5-461f-8753-145dcbdb6c78 | 8b9b3491-f083-4485-8374-258372f3db35 | 216f9481-4c9d-4530-b865-51cedfa4b8e7 | attached |
+--------------------------------------+--------------------------------------+--------------------------------------+----------+

Show the details of a Cinder volume attachment from microversion
>= 3.27:

$ openstack --os-volume-api-version 3.27 volume attachment show d338fb38-cfd5-461f-8753-145dcbdb6c78
+-------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Field       | Value                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
+-------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ID          | d338fb38-cfd5-461f-8753-145dcbdb6c78                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Volume ID   | 8b9b3491-f083-4485-8374-258372f3db35                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Instance ID | 216f9481-4c9d-4530-b865-51cedfa4b8e7                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Status      | attached                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Attach Mode | rw                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Attached At | 2021-09-14T13:03:38.000000                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Detached At |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Properties  | access_mode='rw', attachment_id='d338fb38-cfd5-461f-8753-145dcbdb6c78', auth_method='CHAP', auth_password='4XyNNFV2TLPhKXoP', auth_username='jsBMQhWZJXupA4eWHLQG', cacheable='False', driver_volume_type='iscsi', encrypted='False', qos_specs=, target_discovered='False', target_iqn='iqn.2010-10.org.openstack:volume-8b9b3491-f083-4485-8374-258372f3db35', target_lun='0', target_portal='192.168.122.99:3260', volume_id='8b9b3491-f083-4485-8374-258372f3db35' |
+-------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

Refresh a volume
attachment with nova-manage

24.0.0 (Xena)

Admins may also refresh an existing volume attachment using the
following nova-manage commands.

Note

Users can also refresh volume attachments by shelving and later
unshelving their instances. The following is an alternative to that
workflow and useful for admins when having to mass refresh attachments
across an environment.

Note

Future work will look into introducing an os-refresh admin API that
will include orchestrating the shutdown of an instance and refreshing
volume attachments among other things.

To begin the admin can use the volume_attachment show subcommand to dump
existing details of the attachment directly from the Nova database. This
includes the stashed connection_info not
shared by the API.

$ nova-manage volume_attachment show 216f9481-4c9d-4530-b865-51cedfa4b8e7 8b9b3491-f083-4485-8374-258372f3db35 --json | jq .attachment_id
"d338fb38-cfd5-461f-8753-145dcbdb6c78"

If the stored connection_info or attachment_id are incorrect then the admin may
want to refresh the attachment to the compute host entirely by
recreating the Cinder volume attachment record(s) and pulling down fresh
connection_info. To do this we first need
to ensure the instance is stopped:

$ openstack server stop 216f9481-4c9d-4530-b865-51cedfa4b8e7

Once stopped the host connector of the compute hosting the instance
has to be fetched using the volume_attachment
get_connector
subcommand:

root@compute $ nova-manage volume_attachment get_connector --json > connector.json

Note

Future work will remove this requirement and incorperate the
gathering of the host connector into the main refresh command.
Unfortunatley until then it must remain a seperate manual step.

We can then provide this connector to the volume_attachment refresh subcommand. This
command will connect to the compute, disconnect any host volume
connections, delete the existing Cinder volume attachment, recreate the
volume attachment and finally update Nova’s database.

$ nova-manage volume_attachment refresh 216f9481-4c9d-4530-b865-51cedfa4b8e7 8b9b3491-f083-4485-8374-258372f3db35 connector.json

The Cinder volume attachment and connection_info stored in the Nova
database should now be updated:

$ nova-manage volume_attachment show 216f9481-4c9d-4530-b865-51cedfa4b8e7 8b9b3491-f083-4485-8374-258372f3db35 --json | jq .attachment_id
"9ce46f49-5cfc-4c6c-b2f0-0287540d3246"

The instance can then be restarted and the event list checked

$ openstack server start $instance

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