Add document for consistency groups
Consistency group support was added to Cinder in Juno, but document has not been provided. This patch is to add document on how to use the consistency group feature. Backport: Juno Change-Id: I99c380027fc854674c3ec6b87336f5a920155dac Closes-Bug: #1400392
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Xing Yang
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<?xml version="1.0" encoding="UTF-8"?>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="consistency-groups">
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<title>Consistency Groups</title>
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<para>Consistency group support is available in OpenStack Block Storage.
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The support is added for creating snapshots of consistency groups.
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This feature leverages the storage level consistency technology.
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It allows snapshots of multiple volumes in the same consistency group
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to be taken at the same point-in-time to ensure data consistency.
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The consistency group operations can be performed using the Block Storage
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command line.</para>
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<note><para>Only Block Storage V2 API supports consistency groups. You can
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specify <literal>--os-volume-api-version 2</literal> when using Block
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Storage command line for consistency group operations.</para></note>
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<para>Before using consistency groups, make sure the Block Storage driver
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that you are running has consistency group support by reading the
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Block Storage manual or consulting the driver maintainer. There are
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a small number of drivers that have implemented this feature. The
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default LVM driver does not support consistency groups yet because
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the consistency technology is not available at the storage level.</para>
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<para>Before using consistency groups, you must change policies for the
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consistency group APIs in the <filename>/etc/cinder/policy.json
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</filename> file. By default, the consistency group APIs are disabled.
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Enable them before running consistency group operations.</para>
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<para>Here are existing policy entries for consistency groups:</para>
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<programlisting language="ini">"consistencygroup:create": "group:nobody",
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"consistencygroup:delete": "group:nobody",
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"consistencygroup:get": "group:nobody",
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"consistencygroup:get_all": "group:nobody",
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"consistencygroup:create_cgsnapshot" : "group:nobody",
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"consistencygroup:delete_cgsnapshot": "group:nobody",
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"consistencygroup:get_cgsnapshot": "group:nobody",
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"consistencygroup:get_all_cgsnapshots": "group:nobody",</programlisting>
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<para>Change them to the following by removing <literal>group:nobody
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</literal> to enable these APIs:</para>
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<programlisting language="ini">"consistencygroup:create": "",
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"consistencygroup:delete": "",
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"consistencygroup:update": "",
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"consistencygroup:get": "",
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"consistencygroup:get_all": "",
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"consistencygroup:create_cgsnapshot" : "",
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"consistencygroup:delete_cgsnapshot": "",
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"consistencygroup:get_cgsnapshot": "",
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"consistencygroup:get_all_cgsnapshots": "",</programlisting>
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<para>Restart Block Storage API service after changing policies.</para>
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<para>The following consistency group operations are supported:</para>
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<itemizedlist>
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<listitem>
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<para>Create a consistency group, given volume types.</para>
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<note><para>A consistency group can support more than
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one volume type. The scheduler is responsible for finding
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a back end that can support all given volume types.</para>
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</note>
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<note><para>A consistency group can only contain volumes
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hosted by the same back end.</para></note>
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<note><para>A consistency group is empty upon its creation.
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Volumes need to be created and added to it later.</para>
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</note>
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</listitem>
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<listitem>
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<para>Show a consistency group.</para>
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</listitem>
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<listitem>
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<para>List consistency groups.</para>
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</listitem>
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<listitem>
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<para>Create a volume and add it to a consistency group,
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given volume type and consistency group id.</para>
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</listitem>
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<listitem>
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<para>Create a snapshot for a consistency group.</para>
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</listitem>
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<listitem>
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<para>Show a snapshot of a consistency group.</para>
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</listitem>
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<listitem>
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<para>List consistency group snapshots.</para>
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</listitem>
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<listitem>
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<para>Delete a snapshot of a consistency group.</para>
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</listitem>
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<listitem>
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<para>Delete a consistency group.</para>
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</listitem>
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</itemizedlist>
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<para>The following operations are not allowed if a volume
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is in a consistency group:</para>
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<itemizedlist>
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<listitem>
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<para>Volume migration.</para>
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</listitem>
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<listitem>
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<para>Volume retype.</para>
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</listitem>
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<listitem>
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<para>Volume deletion.</para>
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<note><para>A consistency group has to be
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deleted as a whole with all the volumes.
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</para></note>
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</listitem>
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</itemizedlist>
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<para>The following operations are not allowed if a
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volume snapshot is in a consistency group snapshot:
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</para>
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<itemizedlist>
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<listitem>
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<para>Volume snapshot deletion.</para>
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<note><para>A consistency group snapshot has
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to be deleted as a whole with all the
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volume snapshots.</para></note>
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</listitem>
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</itemizedlist>
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<para>The details of consistency group operations are shown in the
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following.</para>
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<para>Create a consistency group:</para>
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<screen>cinder consisgroup-create
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[--name name]
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[--description description]
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[--availability-zone availability-zone]
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volume-types</screen>
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<note><para>The parameter <literal>volume-types</literal> is required.
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It can be a list of names or UUIDs of volume types separated by
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commas without spaces in between. For example, <literal>
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volumetype1,volumetype2,volumetype3.</literal>.</para></note>
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<screen><prompt>$</prompt> <userinput>cinder consisgroup-create --name bronzeCG2 volume_type_1</userinput></screen>
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<para></para>
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<screen><computeroutput>+-------------------+--------------------------------------+
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| Property | Value |
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+-------------------+--------------------------------------+
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| availability_zone | nova |
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| created_at | 2014-12-29T12:59:08.000000 |
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| description | None |
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| id | 1de80c27-3b2f-47a6-91a7-e867cbe36462 |
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| name | bronzeCG2 |
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| status | creating |
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+-------------------+--------------------------------------+</computeroutput></screen>
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<para>Show a consistency group:</para>
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<screen><prompt>$</prompt> <userinput>cinder consisgroup-show 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput>
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<computeroutput>+-------------------+--------------------------------------+
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| Property | Value |
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+-------------------+--------------------------------------+
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| availability_zone | nova |
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| created_at | 2014-12-29T12:59:08.000000 |
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| description | None |
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| id | 2a6b2bda-1f43-42ce-9de8-249fa5cbae9a |
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| name | bronzeCG2 |
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| status | available |
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+-------------------+--------------------------------------+</computeroutput></screen>
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<para>List consistency groups:</para>
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<screen><prompt>$</prompt> <userinput>cinder consisgroup-list</userinput>
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<computeroutput>+--------------------------------------+-----------+-----------+
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| ID | Status | Name |
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+--------------------------------------+-----------+-----------+
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| 1de80c27-3b2f-47a6-91a7-e867cbe36462 | available | bronzeCG2 |
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| 3a2b3c42-b612-479a-91eb-1ed45b7f2ad5 | error | bronzeCG |
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+--------------------------------------+-----------+-----------+</computeroutput></screen>
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<para>Create a volume and add it to a consistency group:</para>
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<note><para>When creating a volume and adding it to a consistency
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group, a volume type and a consistency group id must be provided.
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This is because a consistency group can support more than one
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volume type.</para></note>
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<screen><prompt>$</prompt> <userinput>cinder create --volume-type volume_type_1 --name cgBronzeVol --consisgroup-id 1de80c27-3b2f-47a6-91a7-e867cbe36462 1</userinput>
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<computeroutput>+---------------------------------------+----------------------------------------+
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| Property | Value |
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+---------------------------------------+----------------------------------------+
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| attachments | [] |
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| availability_zone | nova |
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| bootable | false |
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| consistencygroup_id | 1de80c27-3b2f-47a6-91a7-e867cbe36462 |
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| created_at | 2014-12-29T13:16:47.000000 |
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| description | None |
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| encrypted | False |
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| id | 5e6d1386-4592-489f-a56b-9394a81145fe |
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| metadata | {} |
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| name | cgBronzeVol |
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| os-vol-host-attr:host | server-1@backend-1#pool-1 |
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| os-vol-mig-status-attr:migstat | None |
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| os-vol-mig-status-attr:name_id | None |
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| os-vol-tenant-attr:tenant_id | 1349b21da2a046d8aa5379f0ed447bed |
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| os-volume-replication:driver_data | None |
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| os-volume-replication:extended_status | None |
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| replication_status | disabled |
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| size | 1 |
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| snapshot_id | None |
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| source_volid | None |
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| status | creating |
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| user_id | 93bdea12d3e04c4b86f9a9f172359859 |
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| volume_type | volume_type_1 |
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+---------------------------------------+----------------------------------------+</computeroutput></screen>
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<para>Create a snapshot for a consistency group:</para>
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<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-create 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput>
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<computeroutput>+---------------------+--------------------------------------+
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| Property | Value |
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+---------------------+--------------------------------------+
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| consistencygroup_id | 1de80c27-3b2f-47a6-91a7-e867cbe36462 |
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| created_at | 2014-12-29T13:19:44.000000 |
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| description | None |
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| id | d4aff465-f50c-40b3-b088-83feb9b349e9 |
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| name | None |
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| status | creating |
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+---------------------+-------------------------------------+</computeroutput></screen>
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<para>Show a snapshot of a consistency group:</para>
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<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-show d4aff465-f50c-40b3-b088-83feb9b349e9</userinput></screen>
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<para>List consistency group snapshots:</para>
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<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-list</userinput>
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<computeroutput>+--------------------------------------+--------+----------+
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| ID | Status | Name |
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+--------------------------------------+--------+----------+
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| 6d9dfb7d-079a-471e-b75a-6e9185ba0c38 | available | None |
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| aa129f4d-d37c-4b97-9e2d-7efffda29de0 | available | None |
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| bb5b5d82-f380-4a32-b469-3ba2e299712c | available | None |
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| d4aff465-f50c-40b3-b088-83feb9b349e9 | available | None |
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+--------------------------------------+--------+----------+</computeroutput></screen>
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<para>Delete a snapshot of a consistency group:</para>
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<screen><prompt>$</prompt> <userinput>cinder cgsnapshot-delete d4aff465-f50c-40b3-b088-83feb9b349e9</userinput></screen>
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<para>Delete a consistency group:</para>
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<note><para>The force flag is needed when there are volumes in the
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consistency group.</para></note>
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<screen><prompt>$</prompt> <userinput>cinder consisgroup-delete --force 1de80c27-3b2f-47a6-91a7-e867cbe36462</userinput></screen>
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</section>
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@ -149,6 +149,7 @@
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targets and add iSCSI initiators to the system.</para>
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</section>
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<xi:include href="blockstorage/section_volume_number_weighter.xml"/>
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<xi:include href="blockstorage/section_consistency_groups.xml"/>
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</section>
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<section xml:id="troubleshooting-cinder-install">
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<title>Troubleshoot your installation</title>
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