openstack-manuals/doc/admin-guide-cloud/ch_blockstorage.xml

<?xml version="1.0" encoding="UTF-8"?>
<chapter 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="managing-volumes">
    <title>Block Storage</title>
    <para>The OpenStack Block Storage service works though the
        interaction of a series of daemon processes named cinder-*
        that reside persistently on the host machine or machines. The
        binaries can all be run from a single node, or spread across
        multiple nodes. They can also be run on the same node as other
        OpenStack services.</para>
    <section xml:id="section_block-storage-intro">
        <title>Introduction to Block Storage</title>
    <para>To administer the OpenStack Block Storage service, it is
        helpful to understand a number of concepts. You must make
        certain choices when you configure the Block Storage service
        in OpenStack. The bulk of the options come down to two
        choices, single node or multi-node install. You can read a
        longer discussion about storage decisions in <link
            xlink:href="http://docs.openstack.org/trunk/openstack-ops/content/storage_decision.html"
            >Storage Decisions</link> in the <citetitle>OpenStack
                Operations Guide</citetitle>.</para>
    <para>The OpenStack Block Storage service enables you to add extra
        block-level storage to your OpenStack Compute instances. This
        service is similar to the Amazon EC2 Elastic Block Storage
        (EBS) offering.</para>
    </section>
    <section xml:id="section_manage-volumes">
    <title>Manage volumes</title>
    <para>The default OpenStack Block Storage service implementation
        is an iSCSI solution that uses Logical Volume Manager (LVM)
        for Linux.</para>
    <note>
        <para>The OpenStack Block Storage service is not a shared
            storage solution like SAN or NFS, where you can attach a
            volume to multiple servers. With the OpenStack Block
            Storage service, you can attach a volume to only one
            instance at a time.</para>
        <para>The OpenStack Block Storage service also provides
            drivers that enable you to use several vendors' back-end
            storage devices, in addition to or instead of the base LVM
            implementation.</para>
    </note>
    <para>The following high-level procedure shows you how to create
        and attach a volume to a server instance.</para>
    <procedure>
        <title>To create and attach a volume to a server
            instance:</title>
        <step><para>You must configure both OpenStack Compute and the
            OpenStack Block Storage service through the
                <filename>cinder.conf</filename> file.</para></step>
        <step>

            <para>Create a volume through the <command>cinder create</command> command. This command
                creates an LV into the volume group (VG) "cinder-volumes." </para>
        </step>

        <step>
            <para>Attach the volume to an instance through the
                    <command>nova volume-attach</command> command.
                This command creates a unique iSCSI IQN that is
                exposed to the compute node.</para>
            <substeps>
                <step>
                    <para>The compute node, which runs the instance, now has an active ISCSI session
                        and new local storage (usually a /dev/sdX disk).</para>
                </step>
                <step>
                    <para>libvirt uses that local storage as storage for the instance. The instance
                        get a new disk, usually a /dev/vdX disk.</para>
                </step>
            </substeps>
        </step>
    </procedure>
    <para>For this particular walk through, there is one cloud
        controller running <systemitem class="service">nova-api</systemitem>,
        <systemitem class="service">nova-scheduler</systemitem>,
        <systemitem class="service">nova-objectstore</systemitem>,
        <literal>nova-network</literal> and
        <literal>cinder-*</literal> services. There are two
        additional compute nodes running
        <systemitem class="service">nova-compute</systemitem>. The walk through uses
        a custom partitioning scheme that carves out 60GB of space
        and labels it as LVM. The network uses
        <literal>FlatManger</literal> is the
        <literal>NetworkManager</literal> setting for
        OpenStack Compute (Nova).</para>
    <para>Please note that the network mode doesn't interfere at
        all with the way cinder works, but networking must be set
        up for cinder to work. Please refer to <link
            xlink:href="http://docs.openstack.org/grizzly/openstack-network/admin/content/">Networking Administration</link> for more
        details.</para>
    <para>To set up Compute to use volumes, ensure that Block
        Storage is installed along with lvm2. This guide describes how to:</para>
    <para>
        <itemizedlist>
            <listitem>
                <para>Troubleshoot your installation.</para>
            </listitem>
            <listitem>
                <para>Back up your Compute volumes.</para>
            </listitem>
        </itemizedlist>
    </para>

    <section xml:id="boot-from-volume">
        <title>Boot from volume</title>
        <para>In some cases, instances can be stored and run from inside volumes. This is explained in further detail in the <link xlink:href="http://docs.openstack.org/user-guide/content/boot_from_volume.html">Boot From Volume</link>
            section of the <citetitle>OpenStack End User Guide</citetitle>.</para>
    </section>

    <xi:include href="section_troubleshoot-cinder.xml"/>
    <xi:include href="section_multi_backend.xml"/>
    <xi:include href="section_backup-block-storage-disks.xml"/>
    <xi:include href="section_volume-migration.xml"/>
    </section>
</chapter>