eff9130445
changed to “so that the services continue to be available” made changes to sentence structure Change-Id: Ib3334c4ec18e2d20d1443a980d8eda5e51c609e0
485 lines
20 KiB
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485 lines
20 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section version="5.0" xml:id="example_architecture-nova"
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xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:ns5="http://www.w3.org/2000/svg"
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xmlns:ns4="http://www.w3.org/1998/Math/MathML"
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xmlns:ns3="http://www.w3.org/1999/xhtml"
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xmlns:ns="http://docbook.org/ns/docbook">
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<?dbhtml stop-chunking?>
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<title>Example Architecture—Legacy Networking (nova)</title>
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<para>This particular example architecture has been upgraded from Grizzly to
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Havana and tested in production environments where many public IP addresses
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are available for assignment to multiple instances. You can find a second
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example architecture that uses OpenStack Networking (neutron) after this
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section. Each example offers high availability, meaning that if a particular
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node goes down, another node with the same configuration can take over the
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tasks so that the services continue to be available.<indexterm class="singular">
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<primary>Havana</primary>
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</indexterm><indexterm class="singular">
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<primary>Grizzly</primary>
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</indexterm></para>
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<section xml:id="overview">
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<title>Overview</title>
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<para>The simplest architecture you can build upon for Compute has a
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single cloud controller and multiple compute nodes. The simplest
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architecture for Object Storage has five nodes: one for identifying users
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and proxying requests to the API, then four for storage itself to provide
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enough replication for eventual consistency. This example architecture
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does not dictate a particular number of nodes, but shows the thinking
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<phrase role="keep-together">and considerations</phrase> that went into
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choosing this architecture including the features <phrase
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role="keep-together">offered</phrase>.<indexterm class="singular">
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<primary>CentOS</primary>
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</indexterm><indexterm class="singular">
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<primary>RDO (Red Hat Distributed OpenStack)</primary>
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</indexterm><indexterm class="singular">
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<primary>Ubuntu</primary>
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</indexterm><indexterm class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>component overview</secondary>
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</indexterm><indexterm class="singular">
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<primary>example architectures</primary>
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<see>legacy networking; OpenStack networking</see>
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</indexterm><indexterm class="singular">
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<primary>Object Storage</primary>
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<secondary>simplest architecture for</secondary>
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</indexterm><indexterm class="singular">
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<primary>Compute</primary>
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<secondary>simplest architecture for</secondary>
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</indexterm></para>
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<section xml:id="overview_components-nova">
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<title>Components</title>
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<informaltable rules="all">
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<col width="40%" />
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<col width="60%" />
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<thead>
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<tr>
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<th>Component</th>
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<th>Details</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td><para>OpenStack release</para></td>
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<td><para>Havana</para></td>
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</tr>
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<tr>
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<td><para>Host operating system</para></td>
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<td><para>Ubuntu 12.04 LTS or Red Hat Enterprise Linux 6.5,
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including derivatives such as CentOS and Scientific
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Linux</para></td>
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</tr>
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<tr>
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<td><para>OpenStack package repository</para></td>
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<td><para><link xlink:href="https://wiki.ubuntu.com/ServerTeam/CloudArchive">Ubuntu Cloud
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Archive</link> or <link
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xlink:href="http://openstack.redhat.com/Frequently_Asked_Questions">RDO</link>*</para></td>
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</tr>
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<tr>
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<td><para>Hypervisor</para></td>
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<td><para>KVM</para></td>
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</tr>
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<tr>
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<td><para>Database</para></td>
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<td><para>MySQL*</para></td>
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</tr>
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<tr>
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<td><para>Message queue</para></td>
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<td><para>RabbitMQ for Ubuntu; Qpid for Red Hat Enterprise Linux
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and derivatives</para></td>
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</tr>
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<tr>
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<td><para>Networking service</para></td>
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<td><para><literal>nova-network</literal></para></td>
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</tr>
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<tr>
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<td><para>Network manager</para></td>
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<td><para>FlatDHCP</para></td>
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</tr>
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<tr>
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<td><para>Single <literal>nova-network</literal> or
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multi-host?</para></td>
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<td><para>multi-host*</para></td>
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</tr>
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<tr>
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<td><para>Image service (glance) back end</para></td>
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<td><para>file</para></td>
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</tr>
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<tr>
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<td><para>Identity (keystone) driver</para></td>
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<td><para>SQL</para></td>
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</tr>
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<tr>
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<td><para>Block Storage (cinder) back end</para></td>
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<td><para>LVM/iSCSI</para></td>
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</tr>
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<tr>
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<td><para>Live Migration back end</para></td>
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<td><para>Shared storage using NFS*</para></td>
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</tr>
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<tr>
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<td><para>Object storage</para></td>
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<td><para>OpenStack Object Storage (swift)</para></td>
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</tr>
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</tbody>
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</informaltable>
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<para>An asterisk (*) indicates when the example architecture deviates
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from the settings of a default installation. We'll offer explanations
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for those deviations next.<indexterm class="singular">
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<primary>objects</primary>
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<secondary>object storage</secondary>
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</indexterm><indexterm class="singular">
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<primary>storage</primary>
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<secondary>object storage</secondary>
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</indexterm><indexterm class="singular">
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<primary>migration</primary>
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</indexterm><indexterm class="singular">
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<primary>live migration</primary>
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</indexterm><indexterm class="singular">
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<primary>IP addresses</primary>
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<secondary>floating</secondary>
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</indexterm><indexterm class="singular">
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<primary>floating IP address</primary>
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</indexterm><indexterm class="singular">
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<primary>storage</primary>
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<secondary>block storage</secondary>
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</indexterm><indexterm class="singular">
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<primary>block storage</primary>
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</indexterm><indexterm class="singular">
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<primary>dashboard</primary>
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</indexterm><indexterm class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>features supported by</secondary>
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</indexterm></para>
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<note>
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<para>The following features of OpenStack are supported by the example
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architecture documented in this guide, but are optional:<itemizedlist
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role="compact">
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<listitem>
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<para><glossterm>Dashboard</glossterm>: You probably want to
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offer a dashboard, but your users may be more interested in API
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access only.</para>
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</listitem>
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<listitem>
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<para><glossterm>Block storage</glossterm>: You don't have to
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offer users block storage if their use case only needs ephemeral
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storage on compute nodes, for example.</para>
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</listitem>
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<listitem>
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<para><glossterm>Floating IP address</glossterm>: Floating IP
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addresses are public IP addresses that you allocate from a
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predefined pool to assign to virtual machines at launch.
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Floating IP address ensure that the public IP address is
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available whenever an instance is booted. Not every organization
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can offer thousands of public floating IP addresses for
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thousands of instances, so this feature is considered
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optional.</para>
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</listitem>
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<listitem>
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<para><glossterm>Live migration</glossterm>: If you need to move
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running virtual machine instances from one host to another with
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little or no service interruption, you would enable live
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migration, but it is considered optional.</para>
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</listitem>
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<listitem>
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<para><glossterm>Object storage</glossterm>: You may choose to
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store machine images on a file system rather than in object
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storage if you do not have the extra hardware for the required
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replication and redundancy that OpenStack Object Storage
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offers.</para>
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</listitem>
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</itemizedlist></para>
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</note>
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</section>
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<section xml:id="rationale">
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<title>Rationale</title>
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<para>This example architecture has been selected based on the current
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default feature set of OpenStack <glossterm>Havana</glossterm>, with an
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emphasis on stability. We believe that many clouds that currently run
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OpenStack in production have made similar choices.<indexterm
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class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>rationale for choice of</secondary>
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</indexterm></para>
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<para>You must first choose the operating system that runs on all of the
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physical nodes. While OpenStack is supported on several distributions of
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Linux, we used <emphasis>Ubuntu 12.04 LTS (Long Term
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Support)</emphasis>, which is used by the majority of the development
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community, has feature completeness compared with other distributions
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and has clear future support plans.</para>
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<para>We recommend that you do not use the default Ubuntu OpenStack
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install packages and instead use the <link
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xlink:href="https://wiki.ubuntu.com/ServerTeam/CloudArchive">Ubuntu Cloud Archive</link>. The
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Cloud Archive is a package repository supported by Canonical that allows
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you to upgrade to future OpenStack releases while remaining on Ubuntu
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12.04.</para>
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<para><emphasis>KVM</emphasis> as a <glossterm>hypervisor</glossterm>
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complements the choice of Ubuntu—being a matched pair in terms of
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support, and also because of the significant degree of attention it
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garners from the OpenStack development community (including the authors,
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who mostly use KVM). It is also feature complete, free from licensing
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charges and restrictions.<indexterm class="singular">
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<primary>kernel-based VM (KVM) hypervisor</primary>
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</indexterm><indexterm class="singular">
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<primary>hypervisors</primary>
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<secondary>KVM</secondary>
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</indexterm></para>
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<para><emphasis>MySQL</emphasis> follows a similar trend. Despite its
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recent change of ownership, this database is the most tested for use
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with OpenStack and is heavily documented. We deviate from the default
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database, <emphasis>SQLite</emphasis>, because SQLite is not an
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appropriate database for production usage.</para>
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<para>The choice of <emphasis>RabbitMQ</emphasis> over other AMQP
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compatible options that are gaining support in OpenStack, such as ZeroMQ
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and Qpid, is due to its ease of use and significant testing in
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production. It also is the only option that supports features such as
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Compute cells. We recommend clustering with RabbitMQ, as it is an
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integral component of the system and fairly simple to implement due to
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its inbuilt nature.<indexterm class="singular">
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<primary>Advanced Message Queuing Protocol (AMQP)</primary>
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</indexterm></para>
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<para>As discussed in previous chapters, there are several options for
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networking in OpenStack Compute. We recommend
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<emphasis>FlatDHCP</emphasis> and to use <emphasis>Multi-Host</emphasis>
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networking mode for high availability, running one
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<code>nova-network</code> daemon per OpenStack compute host. This
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provides a robust mechanism for ensuring network interruptions are
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isolated to individual compute hosts, and allows for the direct use of
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hardware network gateways.</para>
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<para><emphasis>Live Migration</emphasis> is supported by way of shared
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storage, with <emphasis>NFS</emphasis> as the distributed file
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system.</para>
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<para>Acknowledging that many small-scale deployments see running Object
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Storage just for the storage of virtual machine images as too costly, we
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opted for the file back end in the OpenStack Image service (Glance). If
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your cloud will include Object Storage, you can easily add it as a
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back end.</para>
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<para>We chose the <emphasis>SQL back end for Identity</emphasis>
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over others, such as LDAP. This back end is simple
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to install and is robust. The authors acknowledge that many
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installations want to bind with existing directory services and caution
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careful understanding of the <link xlink:href="http://docs.openstack.org/havana/config-reference/content/ch_configuring-openstack-identity.html#configuring-keystone-for-ldap-backend"
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xlink:title="LDAP config options">array of options
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available</link>.</para>
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<para>Block Storage (cinder) is installed natively on external storage
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nodes and uses the <emphasis>LVM/iSCSI plug-in</emphasis>. Most Block
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Storage plug-ins are tied to particular vendor products and
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implementations limiting their use to consumers of those hardware
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platforms, but LVM/iSCSI is robust and stable on commodity
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hardware.</para>
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<?hard-pagebreak ?>
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<para>While the cloud can be run without the <emphasis>OpenStack
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Dashboard</emphasis>, we consider it to be indispensable, not just for
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user interaction with the cloud, but also as a tool for operators.
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Additionally, the dashboard's use of Django makes it a flexible
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framework for <phrase role="keep-together">extension</phrase>.</para>
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</section>
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<section xml:id="neutron">
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<title>Why not use OpenStack Networking?</title>
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<para>This example architecture does not use OpenStack Networking,
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because it does not yet support multi-host networking
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and our organizations (university, government) have access to a large
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range of publicly-accessible IPv4 addresses.<indexterm class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>vs. OpenStack Networking (neutron)</secondary>
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</indexterm></para>
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</section>
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<section xml:id="multi-host-networking">
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<title>Why use multi-host networking?</title>
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<para>In a default OpenStack deployment, there is a single
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<code>nova-network</code> service that runs within the cloud (usually on
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the cloud controller) that provides services such as network address
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translation (NAT), DHCP, and DNS to the guest instances. If the single
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node that runs the <code>nova-network</code> service goes down, you
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cannot access your instances, and the instances cannot access the
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Internet. The single node that runs the <literal>nova-network</literal>
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service can become a bottleneck if excessive network traffic comes in
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and goes out of the cloud.<indexterm class="singular">
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<primary>networks</primary>
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<secondary>multi-host</secondary>
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</indexterm><indexterm class="singular">
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<primary>multi-host networking</primary>
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</indexterm><indexterm class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>benefits of multi-host networking</secondary>
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</indexterm></para>
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<tip>
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<para><link xlink:href="http://docs.openstack.org/havana/install-guide/install/apt/content/nova-network.html">Multi-host</link> is
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a high-availability option for the network configuration, where the
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<literal>nova-network</literal> service is run on every compute node
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instead of running on only a single node.</para>
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</tip>
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</section>
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</section>
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<section xml:id="detailed_desc">
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<title>Detailed Description</title>
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<para>The reference architecture consists of multiple compute nodes, a
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cloud controller, an external NFS storage server for instance storage, and
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an OpenStack Block Storage server for <glossterm>volume</glossterm>
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storage.<indexterm class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>detailed description</secondary>
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</indexterm> A network time service (Network Time Protocol, or NTP)
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synchronizes time on all the nodes. FlatDHCPManager in multi-host mode is
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used for the networking. A logical diagram for this example architecture
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shows which services are running on each node:</para>
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<informalfigure>
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<mediaobject>
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<imageobject>
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<imagedata fileref="http://git.openstack.org/cgit/openstack/operations-guide/plain/doc/openstack-ops/figures/osog_01in01.png"></imagedata>
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</imageobject>
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</mediaobject>
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</informalfigure>
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<para>The cloud controller runs the dashboard, the API services, the
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database (MySQL), a message queue server (RabbitMQ), the scheduler for
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choosing compute resources (<literal>nova-scheduler</literal>), Identity
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services (keystone, <code>nova-consoleauth</code>), Image services
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(<code>glance-api</code>, <code>glance-registry</code>), services for
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console access of guests, and Block Storage services, including the
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scheduler for storage resources (<code>cinder-api</code> and
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<code>cinder-scheduler</code>).<indexterm class="singular">
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<primary>cloud controllers</primary>
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<secondary>duties of</secondary>
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</indexterm></para>
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<para>Compute nodes are where the computing resources are held, and in our
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example architecture, they run the hypervisor (KVM), libvirt (the driver
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for the hypervisor, which enables live migration from node to node),
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<code>nova-compute</code>, <code>nova-api-metadata</code> (generally only
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used when running in multi-host mode, it retrieves instance-specific
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metadata), <code>nova-vncproxy</code>, and
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<code>nova-network</code>.</para>
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<para>The network consists of two switches, one for the management or
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private traffic, and one that covers public access, including floating
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IPs. To support this, the cloud controller and the compute nodes have two
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network cards. The OpenStack Block Storage and NFS storage servers only
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need to access the private network and therefore only need one network
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card, but multiple cards run in a bonded configuration are recommended if
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possible. Floating IP access is direct to the Internet, whereas Flat IP
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access goes through a NAT. To envision the network traffic, use this
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diagram:</para>
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<informalfigure>
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<mediaobject>
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<imageobject>
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<imagedata fileref="http://git.openstack.org/cgit/openstack/operations-guide/plain/doc/openstack-ops/figures/osog_01in02.png"></imagedata>
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</imageobject>
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</mediaobject>
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</informalfigure>
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</section>
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<section xml:id="optional_extensions">
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<title>Optional Extensions</title>
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|
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<para>You can extend this reference architecture as<indexterm
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class="singular">
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<primary>legacy networking (nova)</primary>
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<secondary>optional extensions</secondary>
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</indexterm> follows:</para>
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<itemizedlist role="compact">
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<listitem>
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<para>Add additional cloud controllers (see <xref
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linkend="maintenance" />).</para>
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</listitem>
|
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|
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<listitem>
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<para>Add an OpenStack Storage service (see the Object Storage chapter
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in the <emphasis>OpenStack Installation Guide</emphasis> for your
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distribution).</para>
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</listitem>
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|
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<listitem>
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<para>Add additional OpenStack Block Storage hosts (see <xref
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linkend="maintenance" />).</para>
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</listitem>
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</itemizedlist>
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</section>
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</section>
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