openstack/openstack-manuals
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6481c35844
openstack-manuals/doc/admin-guide-cloud/blockstorage/section_consistency_groups.xml
Xing Yang 89be20126e New consistency group APIs 
In Kilo, two new APIs were added to support consistency groups
in Cinder:
* Modify consistency groups.
* Create consistency group from a snapshot of a consistency group.
This patch adds documentation for the new APIs.

Closes-Bug: 1362882

Change-Id: Ibf9c5dcb5726cea470c5874542ea4df19933179c
2015-04-27 00:55:20 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<section xmlns="http://docbook.org/ns/docbook"
xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:xlink="http://www.w3.org/1999/xlink"
version="5.0"
xml:id="consistency-groups">
<title>Consistency Groups</title>
<para>Consistency group support is available in OpenStack Block Storage.
The support is added for creating snapshots of consistency groups.
This feature leverages the storage level consistency technology.
It allows snapshots of multiple volumes in the same consistency group
to be taken at the same point-in-time to ensure data consistency.
The consistency group operations can be performed using the Block Storage
command line.</para>
<note><para>Only Block Storage V2 API supports consistency groups. You can
specify <literal>--os-volume-api-version 2</literal> when using Block
Storage command line for consistency group operations.</para></note>
<para>Before using consistency groups, make sure the Block Storage driver
that you are running has consistency group support by reading the
Block Storage manual or consulting the driver maintainer. There are
a small number of drivers that have implemented this feature. The
default LVM driver does not support consistency groups yet because
the consistency technology is not available at the storage level.</para>
<para>Before using consistency groups, you must change policies for the
consistency group APIs in the <filename>/etc/cinder/policy.json
</filename> file. By default, the consistency group APIs are disabled.
Enable them before running consistency group operations.</para>
<para>Here are existing policy entries for consistency groups:</para>
<programlisting language="ini">"consistencygroup:create": "group:nobody",
"consistencygroup:delete": "group:nobody",
"consistencygroup:get": "group:nobody",
"consistencygroup:get_all": "group:nobody",
"consistencygroup:create_cgsnapshot" : "group:nobody",
"consistencygroup:delete_cgsnapshot": "group:nobody",
"consistencygroup:get_cgsnapshot": "group:nobody",
"consistencygroup:get_all_cgsnapshots": "group:nobody",</programlisting>
<para>Change them to the following by removing <literal>group:nobody
</literal> to enable these APIs:</para>
<programlisting language="ini">"consistencygroup:create": "",
"consistencygroup:delete": "",
"consistencygroup:update": "",
"consistencygroup:get": "",
"consistencygroup:get_all": "",
"consistencygroup:create_cgsnapshot" : "",
"consistencygroup:delete_cgsnapshot": "",
"consistencygroup:get_cgsnapshot": "",
"consistencygroup:get_all_cgsnapshots": "",</programlisting>
<para>Restart Block Storage API service after changing policies.</para>
<para>The following consistency group operations are supported:</para>
<itemizedlist>
<listitem>
<para>Create a consistency group, given volume types.</para>
<note><para>A consistency group can support more than
one volume type. The scheduler is responsible for finding
a back end that can support all given volume types.</para>
</note>
<note><para>A consistency group can only contain volumes
hosted by the same back end.</para></note>
<note><para>A consistency group is empty upon its creation.
Volumes need to be created and added to it later.</para>
</note>
</listitem>
<listitem>
<para>Show a consistency group.</para>
</listitem>
<listitem>
<para>List consistency groups.</para>
</listitem>
<listitem>
<para>Create a volume and add it to a consistency group,
given volume type and consistency group id.</para>
</listitem>
<listitem>
<para>Create a snapshot for a consistency group.</para>
</listitem>
<listitem>
<para>Show a snapshot of a consistency group.</para>
</listitem>
<listitem>
<para>List consistency group snapshots.</para>
</listitem>
<listitem>
<para>Delete a snapshot of a consistency group.</para>
</listitem>
<listitem>
<para>Delete a consistency group.</para>
</listitem>
<listitem>
<para>Modify a consistency group.</para>
</listitem>
<listitem>
<para>Create a consistency group from the snapshot of another
consistency group.</para>
</listitem>
</itemizedlist>
<para>The following operations are not allowed if a volume
is in a consistency group:</para>
<itemizedlist>
<listitem>
<para>Volume migration.</para>
</listitem>
<listitem>
<para>Volume retype.</para>
</listitem>
<listitem>
<para>Volume deletion.</para>
<note><para>A consistency group has to be
deleted as a whole with all the volumes.
</para></note>
</listitem>
</itemizedlist>
<para>The following operations are not allowed if a
volume snapshot is in a consistency group snapshot:
</para>
<itemizedlist>
<listitem>
<para>Volume snapshot deletion.</para>
<note><para>A consistency group snapshot has
to be deleted as a whole with all the
volume snapshots.</para></note>
</listitem>
</itemizedlist>
<para>The details of consistency group operations are shown in the
following.</para>
<para>Create a consistency group:</para>
<screen>cinder consisgroup-create
[--name name]
[--description description]
[--availability-zone availability-zone]
volume-types</screen>
<note><para>The parameter <literal>volume-types</literal> is required.
It can be a list of names or UUIDs of volume types separated by
commas without spaces in between. For example, <literal>
volumetype1,volumetype2,volumetype3.</literal>.</para></note>
<screen><prompt>$</prompt> <userinput>cinder consisgroup-create --name bronzeCG2 volume_type_1</userinput></screen>
<para></para>
<screen><computeroutput>+-------------------+--------------------------------------+
| Property | Value |
+-------------------+--------------------------------------+
| availability_zone | nova |
| created_at | 2014-12-29T12:59:08.000000 |
| description | None |
| id | 1de80c27-3b2f-47a6-91a7-e867cbe36462 |
| name | bronzeCG2 |
| status | creating |
+-------------------+--------------------------------------+</computeroutput></screen>
<para>Show a consistency group:</para>
<screen><prompt>$</prompt> <userinput>cinder consisgroup-show 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput>
<computeroutput>+-------------------+--------------------------------------+
| Property | Value |
+-------------------+--------------------------------------+
| availability_zone | nova |
| created_at | 2014-12-29T12:59:08.000000 |
| description | None |
| id | 2a6b2bda-1f43-42ce-9de8-249fa5cbae9a |
| name | bronzeCG2 |
| status | available |
+-------------------+--------------------------------------+</computeroutput></screen>
<para>List consistency groups:</para>
<screen><prompt>$</prompt> <userinput>cinder consisgroup-list</userinput>
<computeroutput>+--------------------------------------+-----------+-----------+
| ID | Status | Name |
+--------------------------------------+-----------+-----------+
| 1de80c27-3b2f-47a6-91a7-e867cbe36462 | available | bronzeCG2 |
| 3a2b3c42-b612-479a-91eb-1ed45b7f2ad5 | error | bronzeCG |
+--------------------------------------+-----------+-----------+</computeroutput></screen>
<para>Create a volume and add it to a consistency group:</para>
<note><para>When creating a volume and adding it to a consistency
group, a volume type and a consistency group id must be provided.
This is because a consistency group can support more than one
volume type.</para></note>
<screen><prompt>$</prompt> <userinput>cinder create --volume-type volume_type_1 --name cgBronzeVol --consisgroup-id 1de80c27-3b2f-47a6-91a7-e867cbe36462 1</userinput>
<computeroutput>+---------------------------------------+----------------------------------------+
| Property | Value |
+---------------------------------------+----------------------------------------+
| attachments | [] |
| availability_zone | nova |
| bootable | false |
| consistencygroup_id | 1de80c27-3b2f-47a6-91a7-e867cbe36462 |
| created_at | 2014-12-29T13:16:47.000000 |
| description | None |
| encrypted | False |
| id | 5e6d1386-4592-489f-a56b-9394a81145fe |
| metadata | {} |
| name | cgBronzeVol |
| os-vol-host-attr:host | server-1@backend-1#pool-1 |
| os-vol-mig-status-attr:migstat | None |
| os-vol-mig-status-attr:name_id | None |
| os-vol-tenant-attr:tenant_id | 1349b21da2a046d8aa5379f0ed447bed |
| os-volume-replication:driver_data | None |
| os-volume-replication:extended_status | None |
| replication_status | disabled |
| size | 1 |
| snapshot_id | None |
| source_volid | None |
| status | creating |
| user_id | 93bdea12d3e04c4b86f9a9f172359859 |
| volume_type | volume_type_1 |
+---------------------------------------+----------------------------------------+</computeroutput></screen>
<para>Create a snapshot for a consistency group:</para>
<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-create 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput>
<computeroutput>+---------------------+--------------------------------------+
| Property | Value |
+---------------------+--------------------------------------+
| consistencygroup_id | 1de80c27-3b2f-47a6-91a7-e867cbe36462 |
| created_at | 2014-12-29T13:19:44.000000 |
| description | None |
| id | d4aff465-f50c-40b3-b088-83feb9b349e9 |
| name | None |
| status | creating |
+---------------------+-------------------------------------+</computeroutput></screen>
<para>Show a snapshot of a consistency group:</para>
<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-show d4aff465-f50c-40b3-b088-83feb9b349e9</userinput></screen>
<para>List consistency group snapshots:</para>
<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-list</userinput>
<computeroutput>+--------------------------------------+--------+----------+
| ID | Status | Name |
+--------------------------------------+--------+----------+
| 6d9dfb7d-079a-471e-b75a-6e9185ba0c38 | available | None |
| aa129f4d-d37c-4b97-9e2d-7efffda29de0 | available | None |
| bb5b5d82-f380-4a32-b469-3ba2e299712c | available | None |
| d4aff465-f50c-40b3-b088-83feb9b349e9 | available | None |
+--------------------------------------+--------+----------+</computeroutput></screen>
<para>Delete a snapshot of a consistency group:</para>
<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-delete d4aff465-f50c-40b3-b088-83feb9b349e9</userinput></screen>
<para>Delete a consistency group:</para>
<note><para>The force flag is needed when there are volumes in the
consistency group.</para></note>
<screen><prompt>$</prompt> <userinput>cinder consisgroup-delete --force 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput></screen>
<para>Modify a consistency group:</para>
<screen>cinder consisgroup-update
[--name <replaceable>NAME</replaceable>]
[--description <replaceable>DESCRIPTION</replaceable>]
[--add-volumes <replaceable>UUID1,UUID2,......</replaceable>]
[--remove-volumes <replaceable>UUID3,UUID4,......</replaceable>]
<replaceable>CG</replaceable></screen>
<para>The parameter <replaceable>CG</replaceable> is required.
It can be a name or UUID of a consistency group.
<replaceable>UUID1,UUID2,......</replaceable> are
UUIDs of one or more volumes to be added to the
consistency group, separated by commas. Default is None.
<replaceable>UUID3,UUId4,......</replaceable> are
UUIDs of one or more volumes to be removed from the
consistency group, separated by commas. Default is None.
</para>
<screen><prompt>$</prompt> <userinput>cinder consisgroup-update --name 'new name' --description 'new description' --add-volumes 0b3923f5-95a4-4596-a536-914c2c84e2db,1c02528b-3781-4e32-929c-618d81f52cf3 --remove-volumes 8c0f6ae4-efb1-458f-a8fc-9da2afcc5fb1,a245423f-bb99-4f94-8c8c-02806f9246d8 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput></screen>
<para>Create a consistency group from the snapshot of another consistency
group:
</para>
<screen>cinder consisgroup-create-from-src
[--cgsnapshot <replaceable>CGSNAPSHOT</replaceable>]
[--name <replaceable>NAME</replaceable>]
[--description <replaceable>DESCRIPTION</replaceable>]</screen>
<para>The parameter <replaceable>CGSNAPSHOT</replaceable> is a name
or UUID of a snapshot of a consistency group.</para>
<screen><prompt>$</prompt> <userinput>cinder consisgroup-create-from-src --cgsnapshot 6d9dfb7d-079a-471e-b75a-6e9185ba0c38 --name 'new cg' --description 'new cg from cgsnapshot'</userinput></screen>
</section>
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